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Regular Expression Special Variables
Maintainer: Uri Guttman <uri@sysarch.com> Date: 25 Aug 2000 Last Modified: 22 Sep 2000 Mailing List: perl6-language-regex@perl.org Number: 158 Version: 3 Status: Frozen Frozen since: v2
This RFC addresses ways to make the regex special variables $`, $& and $' not be such pariahs like they are now.
I dropped the local scoping of $`, $& and $' as they are already localized now.
$`, $& and $' are useful variables which are never used by any experienced Perl hacker since they have well known problems with efficiency. Since they are globals, any use of them anywhere in your code forces all regexes to copy their data for potential later referencing by one of them. I will describe some ideas to make this issue go away and return these variables back into the toolbox where they belong.
The copy all regex data problem is solved by a new modifier k (for keep). This tells the regex to do the copy so the 3 vars will work properly. So you would use code like this:
$str = 'prefoopost' ;
if ( $str =~ /foo/k ) {
print "pre is [$`]\n" ;
print "match is [$&]\n" ;
print "post is [$']\n" ;
}
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