#!/usr/bin/perl
use strict;
use warnings;

for my $f (qw(a b)){
        print $f;
        warn ".";
}

##</code><code>##

. at test.pl line 7.
. at test.pl line 7.
ab

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;

for my $f (qw(a b)){
        print $f;
        warn ;
}

##</code><code>##

Warning: something's wrong at test.pl line 7.
Warning: something's wrong at test.pl line 7.
a1

##</code><code>##

$ perl -v

This is perl, v5.8.8 built for i486-linux-gnu-thread-multi