jwkrahn has the solution above, but this is probably what you were trying to do: 
my ($y, $m, $d) = ($s =~ /@{[REGEX]}/)[0, 1, 2];

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However, might I suggest you look at the Readonly module on cpan for an alternative method of creating constants. 
use Data::Dumper;
use Readonly;

use strict;

Readonly my $REGEX => qr/^(\d{4})-(\d{2})-(\d{2})/;

my $s = '2011-02-15';
my ($y, $m, $d) = ($s =~ $REGEX);
print Data::Dumper->Dump([$y, $m, $d], [qw/y m d/]);

[download]

In reply to Re: qr expression defined as constant? by wind
in thread qr expression defined as constant? by Anonymous Monk

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