You really shouldn't be worryomg about use of reseources at this level.
Focus on good style, readability, ease of coding, major
performance issues, and all that other good stuff.
A decent compiler should optimise this sort of construct down
to almost nothing (at most a single extra test), which will not
be noticeable in the overall performance unless it is in the inside
of a very tight loop.
Perl already does some interesting tricks, such as removing
if statements from the code and replacing it with and/or,
so trying to second guess what the byte code looks like is a
waste of time.
The gain you will get in readability and hence reuse,
ability to maintain should outweigh any effect in the code.
--
Brovnik |