Garbage Collection and undef

[Irinotecan]

Hi, Perl neophyte here. I'm wondering how to best go about recovering memory (internal to Perl, of course) for a large array.

my @array = (a, large, array, etc....);
...
#Later, should I do:
undef @array;
#or
@array = ();

#And, if I want to re-use the variable even later, if I use undef, do 
+I:
my @array = (a, new, array);

I guess what my real question is, does undef just force garbage collection, or does it actually un-declare the my definition, so that something later like @array=(...); creates a global? Thanks for any insight.