#!/usr/bin/perl
use strict;
use warnings;
use re qw/eval /;

my $line = 'ab';
my $pattern = q/(.)(?{print ++$counts[0]})^/;

for (0..2) {
    my @counts = (0);

    print "$_: ";
    $line =~ /$pattern/;

    print "; my \@counts = (@counts)\n";
}

{
no strict; no warnings;
print "our \@counts = (".join(",",@counts).")\n";
#print "our \@counts = (@counts)\n";
}