for(my $i = 0; $i < count(@{$self->{keys}}); $i++) {
   my $id = $self->{keys}->[$i];
   if($key =~ m!^$id$!) {
      # do something with the knowledge that we got the correct key
      # then exit out of function using this loop
   }
}
# do something with the knowledge there is no key with that name