You could eval the code into existence. People decry it, but it is one thing that makes dynamic languages so powerful:

#!/usr/bin/perl

use strict;
use warnings;

my $data = "duck";
while(<DATA>) {
    chomp;
    my $code = eval "sub{ \$_[0] =~ $_ }" // die $@;
    if( $code->( $data ) ) {
        print "$data\n";
    }
}

__DATA__
s/duck/luck/
[download]

Produces:

c:\test>junk02
luck
[download]