Perl regex

Computing: Programming: Perl: regex

This article explains regular expressions in terms understandable to mere mortals, and also how to use them in Perl.

Related Articles

• regex: manpage documentation

Details

Special characters in regex:

• . = any character
• * = 0 or more of previous character
• ^ = following string begins the line (except [^...] means "not these characters")
• $ = preceding string ends the line
• [] = list of characters which can satisfy the match at this position
• {} = # of repetitions of previous character
• | = alternatives
• + = 1 or more of previous character
• a-b = range of characters from a to b (must be inside [] to be position-sensitive?)

Operators used to invoke regex:

• =~ returns TRUE if pattern matches
• !~ returns FALSE if pattern matches
• s/pattern/replacement/ replaces pattern with replacement

Examples

• Replace "thingy" with "stuffs" in $string:
  • $string =~ s/thingy/stuffs/;
• Keep only the part of $string before the final "/" (using "|" as the delimiter instead of "/"):
  • $string =~ s|(.*)/[^/]*|$1|;
• ...before the final "-":
  • $string =~ s|(.*)-[^-]*|$1|;
• ...before the final ".":
  • $string =~ s|(.*)\.[^\.]*|$1|;
• ...after the final "."
  • $string =~ s|^.+\.(.+$)|$1|;