If you happen to be working on a particularly large string you can just inch your way across which does away with the temporary list e.g

while($str =~ /\G(.)/gs) { ... }

## or with substr()

my $i = 0;
while( defined(my $c = substr $str, $i++, 1 )) { ... }
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See. perlop, perlre and substr for more info.