That is true. Does that also mean that it would be more efficient to write

foreach my $text_id (keys %hash2) {
  if ($hash2{$text_id} =~ $match) {
    ...
  }
}
[download]

because then you copy nothing? If this is the case I was fooled by someone else (not in this thread) who said that using each was more efficient than using for/foreach...
Your second suggestion would, however, not work because there is no guarantee the strings are unique (in fact, I am certain they are not).
Thanks.