in reply to CPU cycles DO NOT MATTER!
programming is about algorithms.
fortunately, perl does a lot of work for you by offering
data structures like hashes for free. but you should still
have a clue what takes time and what not. you should know
about algorithms in general and also a bit about the
performance of the language you program in.
cpu cycles can matter faster than you think. if you program
an application framework that uses modules, you can
program for maximum maintainability. if you program a
module which gets executed by a framework very often you
might want to benchmark a bit. think about DBI. imagine
it was written in pureperl and without any care for
performance - oh my god, database interaction
would be soo slow in perl. if no module author would care
about speed, perl itself would be slow because cpan is
part of the language somehow. i agree that a very small
difference doesn't usually matter because it might be just
a platform/version issue that changes in the next version,
but to know how to benchmark and to get a feeling about
efficiency does not hurt.