I'd like to alter your test just a little bit to prove a point. Trying to code to the implementation of a language just isn't wise. Observe:

my @foo = (0..100000);
my @t;
foreach my $f (@foo) {
  # comment/uncomment the next lines to change behaviors
  $f.="";
  push(@t, $f+0);
}
system("ps auxwwww | grep perl");
sleep(10);
exit(0);
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The problem is that the memory saved by trying coerce the scalar back to a number to save memory doesn't always work. For example, if the scalar has been used in a string before you don't get the memory back:

• With "push(@t, $f+0)" only: Process size: 12716
• With "push(@t, $f."")" only: process size: 15432
• With "$f.=""; push(@t, $f+0)" : process size 14276

In this case (I believe) that perl remembers having done an number->string conversion and caches the value to prevent having to do it again (or have I got that backwards..?). At any rate, trying to outsmart the interpreter doesn't always work and starts awful cargo-cult beliefs.