$constraint =~ m@
   ^\s*        # skip all whitespace at beginning
   (
       /.+/            # capture the custom regex
       |m(.).+\2    # does this capture the ops? What does the |m do? 
+why is the (.) and \2 in there?
   )
   [cgimosx]*    # ?? don't understand what this is for. what are we t
+rying to match? I thought the ops were matched above
   \s*$        # skip all whitespace at end
   @x

[download]
 regexes can be in a number of ways. one, is the familiar /regex/flags. Another, is with the m// operator, which can have any thing instead of the "/". I think there are some other ways as well, but those are not matched by this regex.

the m(.).+\2 part of the regex is for matching m// type regexes. it says "Match an 'm', followed by any character (the delimiter), followed by at least one character (the regex itself), until you reach the delimiter again". a "\2" is a of using backreferences in regexes. It matches "whatever was in the 2nd set of ()s".

See man perlop for more details.

-- Dan

In reply to Re: A Regex to identify Regex's / Compiling a regex by zigdon
in thread A Regex to identify Regex's / Compiling a regex by knowmad

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