...
if (/^[^yhnujmikolp]+$/i) {
...

##</code><code>##

@ARGV = qw(/usr/dict/words);
my $longest = "";
while (<>) {
  next unless length > length $longest; # too short
  next if /[^qwertasdfgzxcvb\n]/i; # wrong hand
  $longest = $_;
}
print $longest;