0: 12; @counts = (0)
1: 34; @counts = (0)
2: 56; @counts = (0)
@main::counts = (6)

##</code><code>##

#!/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";
}

##</code><code>##

In string, @counts now must be written as \@counts at .\counts.pl line 22, near "our \@counts = (@counts"
Execution of .\counts.pl aborted due to compilation errors.