use strict; 
use warnings; 
my $X = "a1b2c3d4e5"; # or use File::Slurp
my $s = "(\\w\\d)"; # my pattern match $s
my $m = qr/$s/; # compiled to a regular expression $m

my $counter = 0;

while($X=~s/$m//){
        ++$counter;
        next unless $counter > 32766; # wait for it...
        print "this is the $counter iteration, got $1 \n";
}