Do you realise you are using the global hashes in your subroutine instead of the references being passed?

@array_es = split ' ', $hash_es{$string_es};
@array_en = split ' ', $hash_en{$string_en};
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It is probably a bad idea to use the same name for your reference as your global hashes. The code should be:

@array_es = split ' ', $hash_es->{$string_es};
@array_en = split ' ', $hash_en->{$string_en};
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I doubt it would make any difference to the performance however.

In theory ($#array_es+1) is slightly slower than (@array_es) used in scalar context, but again I doubt it would make much difference.