When I need to allocate variables for a limited time, for example when I need them in just a snippet of code, I usually prefer blocks and lexicals instead of undefing. For example:

{
  my @needed_here = get_array() ;

  # do something with data, e.g.
  coffee(@needed_here) ;
}

# you are no more @needed_here ;-)
[download]

As soon as you get out of the block, @needed_here "disappears" (unless you saved some reference to it, for example in a closure)

I prefer this way instead of undefing because it looks clearer to me --when I need the variable, it's there, when I need it no more it goes away (instead of staying around undefined).

If you are interested in this approach, you could take a look at "Private Variables via my()" in perlsub

Ciao!
--bronto

# Another Perl edition of a song:
# The End, by The Beatles
END {
  $you->take($love) eq $you->made($love) ;
}