Constants are transformed into subroutines (at least in some cases, I'm not too familiar with them at all). So one possibility of what to do is get a subroutine call inside your regex. Looking at the perldocs for constant and perlre, I came up with this working code. It uses a highly experimental regex feature, so you probably won't want to use this. Take a look at the perlre documentation to learn more about what the (??{}) construct does. It worked for me, so here it is. 

#!/usr/bin/perl -w
$|++;

use strict;
use constant EXTENSION => '.txt';

my $file = shift;
die sprintf(
  'cannot match "%s" extension in "%s"', EXTENSION, $file
) unless $file =~ /(??{EXTENSION()})\z/;

[download]

Update: I figure I'd cross this out just because you really don't want to use an experimental feature, do you? As discovered with the help of Zed_Lopez, you should really use something like this regex snippet. Or, follow perrin's advice and just use variables instead of constants :)

In reply to Re: constants within regular expression? by Coruscate
in thread constants within regular expression? by Anonymous Monk

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