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PERLTODO(1)                           Perl Programmers Reference Guide                           PERLTODO(1)



NAME
       perltodo - Perl TO-DO List

DESCRIPTION
       This is a list of wishes for Perl. The tasks we think are smaller or easier are listed first. Anyone
       is welcome to work on any of these, but it's a good idea to first contact perl5-porters@perl.org to
       avoid duplication of effort. By all means contact a pumpking privately first if you prefer.

       Whilst patches to make the list shorter are most welcome, ideas to add to the list are also
       encouraged. Check the perl5-porters archives for past ideas, and any discussion about them. One set
       of archives may be found at:

           http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/

       What can we offer you in return? Fame, fortune, and everlasting glory? Maybe not, but if your patch
       is incorporated, then we'll add your name to the AUTHORS file, which ships in the official
       distribution. How many other programming languages offer you 1 line of immortality?

Tasks that only need Perl knowledge
       Remove duplication of test setup.

       Schwern notes, that there's duplication of code - lots and lots of tests have some variation on the
       big block of $Is_Foo checks.  We can safely put this into a file, change it to build an %Is hash and
       require it.  Maybe just put it into test.pl. Throw in the handy tainting subroutines.

       merge common code in installperl and installman

       There are some common subroutines and a common "BEGIN" block in installperl and installman. These
       should probably be merged. It would also be good to check for duplication in all the utility scripts
       supplied in the source tarball. It might be good to move them all to a subdirectory, but this would
       require careful checking to find all places that call them, and change those correctly.

       common test code for timed bail out

       Write portable self destruct code for tests to stop them burning CPU in infinite loops. This needs to
       avoid using alarm, as some of the tests are testing alarm/sleep or timers.

       POD -> HTML conversion in the core still sucks

       Which is crazy given just how simple POD purports to be, and how simple HTML can be. It's not
       actually as simple as it sounds, particularly with the flexibility POD allows for "=item", but it
       would be good to improve the visual appeal of the HTML generated, and to avoid it having any
       validation errors. See also "make HTML install work", as the layout of installation tree is needed to
       improve the cross-linking.

       The addition of "Pod::Simple" and its related modules may make this task easier to complete.

       merge checkpods and podchecker

       pod/checkpods.PL (and "make check" in the pod/ subdirectory) implements a very basic check for pod
       files, but the errors it discovers aren't found by podchecker. Add this check to podchecker, get rid
       of checkpods and have "make check" use podchecker.

       perlmodlib.PL rewrite

       Currently perlmodlib.PL needs to be run from a source directory where perl has been built, or some
       modules won't be found, and others will be skipped. Make it run from a clean perl source tree (so
       it's reproducible).

       Parallel testing

       (This probably impacts much more than the core: also the Test::Harness and TAP::* modules on CPAN.)

       The core regression test suite is getting ever more comprehensive, which has the side effect that it
       takes longer to run. This isn't so good. Investigate whether it would be feasible to give the harness
       script the option of running sets of tests in parallel. This would be useful for tests in t/op/*.t
       and t/uni/*.t and maybe some sets of tests in lib/.

       Questions to answer

       1.  How does screen layout work when you're running more than one test?

       2.  How does the caller of test specify how many tests to run in parallel?

       3.  How do setup/teardown tests identify themselves?

       Pugs already does parallel testing - can their approach be re-used?

       Make Schwern poorer

       We should have tests for everything. When all the core's modules are tested, Schwern has promised to
       donate to $500 to TPF. We may need volunteers to hold him upside down and shake vigorously in order
       to actually extract the cash.

       Improve the coverage of the core tests

       Use Devel::Cover to ascertain the core modules's test coverage, then add tests that are currently
       missing.

       test B

       A full test suite for the B module would be nice.

       Deparse inlined constants

       Code such as this

           use constant PI => 4;
           warn PI

       will currently deparse as

           use constant ('PI', 4);
           warn 4;

       because the tokenizer inlines the value of the constant subroutine "PI".  This allows various compile
       time optimisations, such as constant folding and dead code elimination. Where these haven't happened
       (such as the example above) it ought be possible to make B::Deparse work out the name of the original
       constant, because just enough information survives in the symbol table to do this. Specifically, the
       same scalar is used for the constant in the optree as is used for the constant subroutine, so by
       iterating over all symbol tables and generating a mapping of SV address to constant name, it would be
       possible to provide B::Deparse with this functionality.

       A decent benchmark

       "perlbench" seems impervious to any recent changes made to the perl core. It would be useful to have
       a reasonable general benchmarking suite that roughly represented what current perl programs do, and
       measurably reported whether tweaks to the core improve, degrade or don't really affect performance,
       to guide people attempting to optimise the guts of perl. Gisle would welcome new tests for perlbench.

       fix tainting bugs

       Fix the bugs revealed by running the test suite with the "-t" switch (via "make test.taintwarn").

       Dual life everything

       As part of the "dists" plan, anything that doesn't belong in the smallest perl distribution needs to
       be dual lifed. Anything else can be too. Figure out what changes would be needed to package that
       module and its tests up for CPAN, and do so. Test it with older perl releases, and fix the problems
       you find.

       To make a minimal perl distribution, it's useful to look at t/lib/commonsense.t.

       Improving "threads::shared"

       Investigate whether "threads::shared" could share aggregates properly with only Perl level changes to
       shared.pm

       POSIX memory footprint

       Ilya observed that use POSIX; eats memory like there's no tomorrow, and at various times worked to
       cut it down. There is probably still fat to cut out - for example POSIX passes Exporter some very
       memory hungry data structures.

       embed.pl/makedef.pl

       There is a script embed.pl that generates several header files to prefix all of Perl's symbols in a
       consistent way, to provide some semblance of namespace support in "C". Functions are declared in
       embed.fnc, variables in interpvar.h. Quite a few of the functions and variables are conditionally
       declared there, using "#ifdef". However, embed.pl doesn't understand the C macros, so the rules about
       which symbols are present when is duplicated in makedef.pl. Writing things twice is bad, m'kay.  It
       would be good to teach "embed.pl" to understand the conditional compilation, and hence remove the
       duplication, and the mistakes it has caused.

       use strict; and AutoLoad

       Currently if you write

           package Whack;
           use AutoLoader 'AUTOLOAD';
           use strict;
           1;
           __END__
           sub bloop {
               print join (' ', No, strict, here), "!\n";
           }

       then "use strict;" isn't in force within the autoloaded subroutines. It would be more consistent (and
       less surprising) to arrange for all lexical pragmas in force at the __END__ block to be in force
       within each autoloaded subroutine.

       There's a similar problem with SelfLoader.

Tasks that need a little sysadmin-type knowledge
       Or if you prefer, tasks that you would learn from, and broaden your skills base...

       make HTML install work

       There is an "installhtml" target in the Makefile. It's marked as "experimental". It would be good to
       get this tested, make it work reliably, and remove the "experimental" tag. This would include

       1.  Checking that cross linking between various parts of the documentation works.  In particular that
           links work between the modules (files with POD in lib/) and the core documentation (files in
           pod/)

       2.  Work out how to split "perlfunc" into chunks, preferably one per function group, preferably with
           general case code that could be used elsewhere.  Challenges here are correctly identifying the
           groups of functions that go together, and making the right named external cross-links point to
           the right page. Things to be aware of are "-X", groups such as "getpwnam" to "endservent", two or
           more "=items" giving the different parameter lists, such as

               =item substr EXPR,OFFSET,LENGTH,REPLACEMENT
               =item substr EXPR,OFFSET,LENGTH
               =item substr EXPR,OFFSET

           and different parameter lists having different meanings. (eg "select")

       compressed man pages

       Be able to install them. This would probably need a configure test to see how the system does
       compressed man pages (same directory/different directory?  same filename/different filename), as well
       as tweaking the installman script to compress as necessary.

       Add a code coverage target to the Makefile

       Make it easy for anyone to run Devel::Cover on the core's tests. The steps to do this manually are
       roughly

       •   do a normal "Configure", but include Devel::Cover as a module to install (see INSTALL for how to
           do this)

       •

               make perl

       •

               cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib harness

       •   Process the resulting Devel::Cover database

       This just give you the coverage of the .pms. To also get the C level coverage you need to

       •   Additionally tell "Configure" to use the appropriate C compiler flags for "gcov"

       •

               make perl.gcov

           (instead of "make perl")

       •   After running the tests run "gcov" to generate all the .gcov files.  (Including down in the
           subdirectories of ext/

       •   (From the top level perl directory) run "gcov2perl" on all the ".gcov" files to get their stats
           into the cover_db directory.

       •   Then process the Devel::Cover database

       It would be good to add a single switch to "Configure" to specify that you wanted to perform perl
       level coverage, and another to specify C level coverage, and have "Configure" and the Makefile do all
       the right things automatically.

       Make Config.pm cope with differences between built and installed perl

       Quite often vendors ship a perl binary compiled with their (pay-for) compilers.  People install a
       free compiler, such as gcc. To work out how to build extensions, Perl interrogates %Config, so in
       this situation %Config describes compilers that aren't there, and extension building fails. This
       forces people into choosing between re-compiling perl themselves using the compiler they have, or
       only using modules that the vendor ships.

       It would be good to find a way teach "Config.pm" about the installation setup, possibly involving
       probing at install time or later, so that the %Config in a binary distribution better describes the
       installed machine, when the installed machine differs from the build machine in some significant way.

       linker specification files

       Some platforms mandate that you provide a list of a shared library's external symbols to the linker,
       so the core already has the infrastructure in place to do this for generating shared perl libraries.
       My understanding is that the GNU toolchain can accept an optional linker specification file, and
       restrict visibility just to symbols declared in that file. It would be good to extend makedef.pl to
       support this format, and to provide a means within "Configure" to enable it. This would allow Unix
       users to test that the export list is correct, and to build a perl that does not pollute the global
       namespace with private symbols.

       Cross-compile support

       Currently "Configure" understands "-Dusecrosscompile" option. This option arranges for building
       "miniperl" for TARGET machine, so this "miniperl" is assumed then to be copied to TARGET machine and
       used as a replacement of full "perl" executable.

       This could be done little differently. Namely "miniperl" should be built for HOST and then full
       "perl" with extensions should be compiled for TARGET.  This, however, might require extra trickery
       for %Config: we have one config first for HOST and then another for TARGET.  Tools like MakeMaker
       will be mightily confused.  Having around two different types of executables and libraries (HOST and
       TARGET) makes life interesting for Makefiles and shell (and Perl) scripts.  There is $Config{run},
       normally empty, which can be used as an execution wrapper.  Also note that in some
       cross-compilation/execution environments the HOST and the TARGET do not see the same filesystem(s),
       the $Config{run} may need to do some file/directory copying back and forth.

       roffitall

       Make pod/roffitall be updated by pod/buildtoc.

Tasks that need a little C knowledge
       These tasks would need a little C knowledge, but don't need any specific background or experience
       with XS, or how the Perl interpreter works

       Exterminate PL_na!

       "PL_na" festers still in the darkest corners of various typemap files.  It needs to be exterminated,
       replaced by a local variable of type "STRLEN".

       Modernize the order of directories in @INC

       The way @INC is laid out by default, one cannot upgrade core (dual-life) modules without overwriting
       files. This causes problems for binary package builders.  One possible proposal is laid out in this
       message: <http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2002-04/msg02380.html>.

       -Duse32bit*

       Natively 64-bit systems need neither -Duse64bitint nor -Duse64bitall.  On these systems, it might be
       the default compilation mode, and there is currently no guarantee that passing no use64bitall option
       to the Configure process will build a 32bit perl. Implementing -Duse32bit* options would be nice for
       perl 5.12.

       Make it clear from -v if this is the exact official release

       Currently perl from "p4"/"rsync" ships with a patchlevel.h file that usually defines one local patch,
       of the form "MAINT12345" or "RC1". The output of perl -v doesn't report that a perl isn't an official
       release, and this information can get lost in bugs reports. Because of this, the minor version isn't
       bumped up until RC time, to minimise the possibility of versions of perl escaping that believe
       themselves to be newer than they actually are.

       It would be useful to find an elegant way to have the "this is an interim maintenance release" or
       "this is a release candidate" in the terse -v output, and have it so that it's easy for the pumpking
       to remove this just as the release tarball is rolled up. This way the version pulled out of rsync
       would always say "I'm a development release" and it would be safe to bump the reported minor version
       as soon as a release ships, which would aid perl developers.

       This task is really about thinking of an elegant way to arrange the C source such that it's trivial
       for the Pumpking to flag "this is an official release" when making a tarball, yet leave the default
       source saying "I'm not the official release".

       Profile Perl - am I hot or not?

       The Perl source code is stable enough that it makes sense to profile it, identify and optimise the
       hotspots. It would be good to measure the performance of the Perl interpreter using free tools such
       as cachegrind, gprof, and dtrace, and work to reduce the bottlenecks they reveal.

       As part of this, the idea of pp_hot.c is that it contains the hot ops, the ops that are most commonly
       used. The idea is that by grouping them, their object code will be adjacent in the executable, so
       they have a greater chance of already being in the CPU cache (or swapped in) due to being near
       another op already in use.

       Except that it's not clear if these really are the most commonly used ops. So as part of exercising
       your skills with coverage and profiling tools you might want to determine what ops really are the
       most commonly used. And in turn suggest evictions and promotions to achieve a better pp_hot.c.

       Allocate OPs from arenas

       Currently all new OP structures are individually malloc()ed and free()d.  All "malloc"
       implementations have space overheads, and are now as fast as custom allocates so it would both use
       less memory and less CPU to allocate the various OP structures from arenas. The SV arena code can
       probably be re-used for this.

       Note that Configuring perl with "-Accflags=-DPL_OP_SLAB_ALLOC" will use Perl_Slab_alloc() to pack
       optrees into a contiguous block, which is probably superior to the use of OP arenas, esp. from a
       cache locality standpoint.  See "Profile Perl - am I hot or not?".

       Improve win32/wince.c

       Currently, numerous functions look virtually, if not completely, identical in both "win32/wince.c"
       and "win32/win32.c" files, which can't be good.

       Use secure CRT functions when building with VC8 on Win32

       Visual C++ 2005 (VC++ 8.x) deprecated a number of CRT functions on the basis that they were "unsafe"
       and introduced differently named secure versions of them as replacements, e.g. instead of writing

           FILE* f = fopen(__FILE__, "r");

       one should now write

           FILE* f;
           errno_t err = fopen_s(&f, __FILE__, "r");

       Currently, the warnings about these deprecations have been disabled by adding
       -D_CRT_SECURE_NO_DEPRECATE to the CFLAGS. It would be nice to remove that warning suppressant and
       actually make use of the new secure CRT functions.

       There is also a similar issue with POSIX CRT function names like fileno having been deprecated in
       favour of ISO C++ conformant names like _fileno. These warnings are also currently suppressed by
       adding -D_CRT_NONSTDC_NO_DEPRECATE. It might be nice to do as Microsoft suggest here too, although,
       unlike the secure functions issue, there is presumably little or no benefit in this case.

       strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()

       Maybe create a utility that checks after each libperl.a creation that none of the above (nor
       sprintf(), vsprintf(), or *SHUDDER* gets()) ever creep back to libperl.a.

         nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/; print "$o $F[1]" if $F[0] eq "U" && $F[1] =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'

       Note, of course, that this will only tell whether your platform is using those naughty interfaces.

       -D_FORTIFY_SOURCE=2, -fstack-protector

       Recent glibcs support "-D_FORTIFY_SOURCE=2" and recent gcc (4.1 onwards?) supports
       "-fstack-protector", both of which give protection against various kinds of buffer overflow problems.
       These should probably be used for compiling Perl whenever available, Configure and/or hints files
       should be adjusted to probe for the availability of these features and enable them as appropriate.

Tasks that need a knowledge of XS
       These tasks would need C knowledge, and roughly the level of knowledge of the perl API that comes
       from writing modules that use XS to interface to C.

       autovivification

       Make all autovivification consistent w.r.t LVALUE/RVALUE and strict/no strict;

       This task is incremental - even a little bit of work on it will help.

       Unicode in Filenames

       chdir, chmod, chown, chroot, exec, glob, link, lstat, mkdir, open, opendir, qx, readdir, readlink,
       rename, rmdir, stat, symlink, sysopen, system, truncate, unlink, utime, -X.  All these could
       potentially accept Unicode filenames either as input or output (and in the case of system and qx
       Unicode in general, as input or output to/from the shell).  Whether a filesystem - an operating
       system pair understands Unicode in filenames varies.

       Known combinations that have some level of understanding include Microsoft NTFS, Apple HFS+ (In Mac
       OS 9 and X) and Apple UFS (in Mac OS X), NFS v4 is rumored to be Unicode, and of course Plan 9.  How
       to create Unicode filenames, what forms of Unicode are accepted and used (UCS-2, UTF-16, UTF-8), what
       (if any) is the normalization form used, and so on, varies.  Finding the right level of interfacing
       to Perl requires some thought.  Remember that an OS does not implicate a filesystem.

       (The Windows -C command flag "wide API support" has been at least temporarily retired in 5.8.1, and
       the -C has been repurposed, see perlrun.)

       Most probably the right way to do this would be this: "Virtualize operating system access".

       Unicode in %ENV

       Currently the %ENV entries are always byte strings.  See "Virtualize operating system access".

       Unicode and glob()

       Currently glob patterns and filenames returned from File::Glob::glob() are always byte strings.  See
       "Virtualize operating system access".

       Unicode and lc/uc operators

       Some built-in operators ("lc", "uc", etc.) behave differently, based on what the internal encoding of
       their argument is. That should not be the case. Maybe add a pragma to switch behaviour.

       use less 'memory'

       Investigate trade offs to switch out perl's choices on memory usage.  Particularly perl should be
       able to give memory back.

       This task is incremental - even a little bit of work on it will help.

       Re-implement ":unique" in a way that is actually thread-safe

       The old implementation made bad assumptions on several levels. A good 90% solution might be just to
       make ":unique" work to share the string buffer of SvPVs. That way large constant strings can be
       shared between ithreads, such as the configuration information in Config.

       Make tainting consistent

       Tainting would be easier to use if it didn't take documented shortcuts and allow taint to "leak"
       everywhere within an expression.

       readpipe(LIST)

       system() accepts a LIST syntax (and a PROGRAM LIST syntax) to avoid running a shell. readpipe() (the
       function behind qx//) could be similarly extended.

       Audit the code for destruction ordering assumptions

       Change 25773 notes

           /* Need to check SvMAGICAL, as during global destruction it may be that
              AvARYLEN(av) has been freed before av, and hence the SvANY() pointer
              is now part of the linked list of SV heads, rather than pointing to
              the original body.  */
           /* FIXME - audit the code for other bugs like this one.  */

       adding the "SvMAGICAL" check to

           if (AvARYLEN(av) && SvMAGICAL(AvARYLEN(av))) {
               MAGIC *mg = mg_find (AvARYLEN(av), PERL_MAGIC_arylen);

       Go through the core and look for similar assumptions that SVs have particular types, as all bets are
       off during global destruction.

       Extend PerlIO and PerlIO::Scalar

       PerlIO::Scalar doesn't know how to truncate().  Implementing this would require extending the PerlIO
       vtable.

       Similarly the PerlIO vtable doesn't know about formats (write()), or about stat(), or
       chmod()/chown(), utime(), or flock().

       (For PerlIO::Scalar it's hard to see what e.g. mode bits or ownership would mean.)

       PerlIO doesn't do directories or symlinks, either: mkdir(), rmdir(), opendir(), closedir(),
       seekdir(), rewinddir(), glob(); symlink(), readlink().

       See also "Virtualize operating system access".

       -C on the #! line

       It should be possible to make -C work correctly if found on the #! line, given that all perl command
       line options are strict ASCII, and -C changes only the interpretation of non-ASCII characters, and
       not for the script file handle. To make it work needs some investigation of the ordering of function
       calls during startup, and (by implication) a bit of tweaking of that order.

       Propagate const outwards from Perl_moreswitches()

       Change 32057 changed the parameter and return value of "Perl_moreswitches()" from <char *> to <const
       char *>. It should now be possible to propagate const-correctness outwards to "S_parse_body()",
       "Perl_moreswitches()" and "Perl_yylex()".

       Duplicate logic in S_method_common() and Perl_gv_fetchmethod_autoload()

       A comment in "S_method_common" notes

               /* This code tries to figure out just what went wrong with
                  gv_fetchmethod.  It therefore needs to duplicate a lot of
                  the internals of that function.  We can't move it inside
                  Perl_gv_fetchmethod_autoload(), however, since that would
                  cause UNIVERSAL->can("NoSuchPackage::foo") to croak, and we
                  don't want that.
               */

       If "Perl_gv_fetchmethod_autoload" gets rewritten to take (more) flag bits, then it ought to be
       possible to move the logic from "S_method_common" to the "right" place. When making this change it
       would probably be good to also pass in at least the method name length, if not also pre-computed hash
       values when known. (I'm contemplating a plan to pre-compute hash values for common fixed strings such
       as "ISA" and pass them in to functions.)

       Organize error messages

       Perl's diagnostics (error messages, see perldiag) could use reorganizing and formalizing so that each
       error message has its stable-for-all-eternity unique id, categorized by severity, type, and
       subsystem.  (The error messages would be listed in a datafile outside of the Perl source code, and
       the source code would only refer to the messages by the id.)  This clean-up and regularizing should
       apply for all croak() messages.

       This would enable all sorts of things: easier translation/localization of the messages (though please
       do keep in mind the caveats of Locale::Maketext about too straightforward approaches to translation),
       filtering by severity, and instead of grepping for a particular error message one could look for a
       stable error id.  (Of course, changing the error messages by default would break all the existing
       software depending on some particular error message...)

       This kind of functionality is known as message catalogs.  Look for inspiration for example in the
       catgets() system, possibly even use it if available-- but only if available, all platforms will not
       have catgets().

       For the really pure at heart, consider extending this item to cover also the warning messages (see
       perllexwarn, "warnings.pl").

Tasks that need a knowledge of the interpreter
       These tasks would need C knowledge, and knowledge of how the interpreter works, or a willingness to
       learn.

       UTF-8 revamp

       The handling of Unicode is unclean in many places. For example, the regexp engine matches in Unicode
       semantics whenever the string or the pattern is flagged as UTF-8, but that should not be dependent on
       an internal storage detail of the string. Likewise, case folding behaviour is dependent on the UTF8
       internal flag being on or off.

       Properly Unicode safe tokeniser and pads.

       The tokeniser isn't actually very UTF-8 clean. "use utf8;" is a hack - variable names are stored in
       stashes as raw bytes, without the utf-8 flag set. The pad API only takes a "char *" pointer, so
       that's all bytes too. The tokeniser ignores the UTF-8-ness of "PL_rsfp", or any SVs returned from
       source filters.  All this could be fixed.

       state variable initialization in list context

       Currently this is illegal:

           state ($a, $b) = foo();

       In Perl 6, "state ($a) = foo();" and "(state $a) = foo();" have different semantics, which is tricky
       to implement in Perl 5 as currently they produce the same opcode trees. The Perl 6 design is firm, so
       it would be good to implement the necessary code in Perl 5. There are comments in
       "Perl_newASSIGNOP()" that show the code paths taken by various assignment constructions involving
       state variables.

       Implement $value ~~ 0 .. $range

       It would be nice to extend the syntax of the "~~" operator to also understand numeric (and maybe
       alphanumeric) ranges.

       A does() built-in

       Like ref(), only useful. It would call the "DOES" method on objects; it would also tell whether
       something can be dereferenced as an array/hash/etc., or used as a regexp, etc.
       <http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-03/msg00481.html>

       Tied filehandles and write() don't mix

       There is no method on tied filehandles to allow them to be called back by formats.

       Attach/detach debugger from running program

       The old perltodo notes "With "gdb", you can attach the debugger to a running program if you pass the
       process ID. It would be good to do this with the Perl debugger on a running Perl program, although
       I'm not sure how it would be done." ssh and screen do this with named pipes in /tmp. Maybe we can
       too.

       Optimize away empty destructors

       Defining an empty DESTROY method might be useful (notably in AUTOLOAD-enabled classes), but it's
       still a bit expensive to call. That could probably be optimized.

       LVALUE functions for lists

       The old perltodo notes that lvalue functions don't work for list or hash slices. This would be good
       to fix.

       LVALUE functions in the debugger

       The old perltodo notes that lvalue functions don't work in the debugger. This would be good to fix.

       regexp optimiser optional

       The regexp optimiser is not optional. It should configurable to be, to allow its performance to be
       measured, and its bugs to be easily demonstrated.

       delete &function

       Allow to delete functions. One can already undef them, but they're still in the stash.

       "/w" regex modifier

       That flag would enable to match whole words, and also to interpolate arrays as alternations. With it,
       "/P/w" would be roughly equivalent to:

           do { local $"='|'; /\b(?:P)\b/ }

       See <http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-01/msg00400.html> for the
       discussion.

       optional optimizer

       Make the peephole optimizer optional. Currently it performs two tasks as it walks the optree -genuine optreegenuine
       genuine peephole optimisations, and necessary fixups of ops. It would be good to find an efficient
       way to switch out the optimisations whilst keeping the fixups.

       You WANT *how* many

       Currently contexts are void, scalar and list. split has a special mechanism in place to pass in the
       number of return values wanted. It would be useful to have a general mechanism for this, backwards
       compatible and little speed hit.  This would allow proposals such as short circuiting sort to be
       implemented as a module on CPAN.

       lexical aliases

       Allow lexical aliases (maybe via the syntax "my \$alias = \$foo".

       entersub XS vs Perl

       At the moment pp_entersub is huge, and has code to deal with entering both perl and XS subroutines.
       Subroutine implementations rarely change between perl and XS at run time, so investigate using 2 ops
       to enter subs (one for XS, one for perl) and swap between if a sub is redefined.

       Self-ties

       Self-ties are currently illegal because they caused too many segfaults. Maybe the causes of these
       could be tracked down and self-ties on all types reinstated.

       Optimize away @_

       The old perltodo notes "Look at the "reification" code in "av.c"".

       The yada yada yada operators

       Perl 6's Synopsis 3 says:

       The ... operator is the "yada, yada, yada" list operator, which is used as the body in function
       prototypes. It complains bitterly (by calling fail) if it is ever executed. Variant ??? calls warn,
       and !!! calls die.

       Those would be nice to add to Perl 5. That could be done without new ops.

       Virtualize operating system access

       Implement a set of "vtables" that virtualizes operating system access (open(), mkdir(), unlink(),
       readdir(), getenv(), etc.)  At the very least these interfaces should take SVs as "name" arguments
       instead of bare char pointers; probably the most flexible and extensible way would be for the Perl-facing Perlfacing
       facing interfaces to accept HVs.  The system needs to be per-operating-system and per-file-system
       hookable/filterable, preferably both from XS and Perl level ("Files and Filesystems" in perlport is
       good reading at this point, in fact, all of perlport is.)

       This has actually already been implemented (but only for Win32), take a look at iperlsys.h and
       win32/perlhost.h.  While all Win32 variants go through a set of "vtables" for operating system
       access, non-Win32 systems currently go straight for the POSIX/UNIX-style system/library call.
       Similar system as for Win32 should be implemented for all platforms.  The existing Win32
       implementation probably does not need to survive alongside this proposed new implementation, the
       approaches could be merged.

       What would this give us?  One often-asked-for feature this would enable is using Unicode for
       filenames, and other "names" like %ENV, usernames, hostnames, and so forth.  (See "When Unicode Does
       Not Happen" in perlunicode.)

       But this kind of virtualization would also allow for things like virtual filesystems, virtual
       networks, and "sandboxes" (though as long as dynamic loading of random object code is allowed, not
       very safe sandboxes since external code of course know not of Perl's vtables).  An example of a
       smaller "sandbox" is that this feature can be used to implement per-thread working directories: Win32
       already does this.

       See also "Extend PerlIO and PerlIO::Scalar".

       Investigate PADTMP hash pessimisation

       The peephole optimier converts constants used for hash key lookups to shared hash key scalars. Under
       ithreads, something is undoing this work. See See
       http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2007-09/msg00793.html

Big projects
       Tasks that will get your name mentioned in the description of the "Highlights of 5.12"

       make ithreads more robust

       Generally make ithreads more robust. See also "iCOW"

       This task is incremental - even a little bit of work on it will help, and will be greatly
       appreciated.

       One bit would be to write the missing code in sv.c:Perl_dirp_dup.

       Fix Perl_sv_dup, et al so that threads can return objects.

       iCOW

       Sarathy and Arthur have a proposal for an improved Copy On Write which specifically will be able to
       COW new ithreads. If this can be implemented it would be a good thing.

       (?{...}) closures in regexps

       Fix (or rewrite) the implementation of the "/(?{...})/" closures.

       A re-entrant regexp engine

       This will allow the use of a regex from inside (?{ }), (??{ }) and (?(?{ })|) constructs.

       Add class set operations to regexp engine

       Apparently these are quite useful. Anyway, Jeffery Friedl wants them.

       demerphq has this on his todo list, but right at the bottom.



perl v5.10.0                                     2007-12-18                                      PERLTODO(1)