Just in case others Super Search for an answer to this question and follow merlyns node mentioned first in the result-set, here is the relevant excerpt of the perlfaq6

Found in /usr/lib/perl5/5.8.0/pod/perlfaq6.pod
What's wrong with using grep or map in a void context?

The problem is that both grep and map build a return list, regardless of the context. This means you're making Perl go to the trouble of building a list that you then just throw away. If the list is large, you waste both time and space. If your intent is to iterate over the list then use a for loop for this purpose.

regards,
tomte

Hlade's Law:

If you have a difficult task, give it to a lazy person --
they will find an easier way to do it.