Nice Post. Would the following achieve the same thing without needing "undef"?

# Iterate through all of the genes on a clone
foreach my $gene ( @{ $first_clone->get_all_Genes() } ) {
    my $temp_obj_handle = $gene;
    print $temp_obj_handle->stable_id(), "\n";
}
[download]

Update: Again kudos to BrowserUk.

Although $temp_obj_handle gets re-cycled and it does "go out of scope", it points to the same place as $gene within the loop and $gene does not go "out of scope". Therefore, the $gene reference count is not, "at the end of the day" decremented. End result: The above code does not save memory within the foreach() loop, although the code from BrowserUk does.

At the end of day, does this memory optimization within a for() loop matter at all? I think that it usually does not.

Perl is excellent about re-cycling memory that it has used before. A typical Perl program reaches a max memory usage and then just stays there (provided of course that you don't have memory leaks :-)). There are not any "garbage collection" calls like in Java or C#. In short, this is fine:

foreach my $gene ( @{ $first_clone->get_all_Genes() } ) {
    print $gene->stable_id(), "\n";
}
[download]

I would not worry until there are thousands of new objects being created. A few hundred? => no.

Update again:

Well as with many things in programming, judgment is required. 5 objects might very well consume 1,483 MB of memory. I have no idea of how much memory that a particular $gene->stable_id() will consume... it might be a lot. On other hand, it might not "be much". This is very application specific. I think this thread has pointed out how the memory allocation works and the OP can decide what to do in a particular situation. I personally would use the most simple loop unless there is a reason not to do so. In other words, make things more complicated when it is necessary to do so. "necessary" is application specific.