These sub-expressions modify a regular expression.
(?imnsx-imnsx) | Sets or disables options in mid-pattern. This allows options such as case insensitivity to be turned on or off in the middle of a pattern. For information on specific options, see the Regular Expression Options section. Options changes are effective until the end of the enclosing group. See also the grouping construct (?imnsx-imnsx: ), which is a cleaner form. |
(?# ) | Comment. The comment terminates at the first right parentheses character. |
# [to end of line] | X-mode comment. The comment begins at an unescaped # and continues to the end of the line. (Note that the "x" option must be activated for this kind of comment to be recognized. (This construct is currently experimental). |