Maybe the following will help (and yes im pretty sure this is at least part of the reason for his leak):

#!perl -l

sub F {
    my $foo=bless[];
    print "create:$foo";
    sub T {
      print "T";
      push @$foo,"test";
    }
    print "F";
    push @$foo,"bar";
}

sub DESTROY { print "destroy: @_:@{$_[0]}" }

F;
T;
T;
T;
F;

__END__
create:main=ARRAY(0x15d53d8)
F
T
T
T
create:main=ARRAY(0x1a4550c)
F
destroy: main=ARRAY(0x1a4550c):bar
destroy: main=ARRAY(0x15d53d8):bar test test test
[download]

T only once shares the same $foo with F, right at the beginning. The first time the sub executes it binds T as a closure to the original $foo and never rebinds it. And since T contains a reference to that $foo, and because T exists in the package table $foo wont be freed until T is destroyed causing $foo's refcount to drop. Thus the OP probably has a number of vars that are filling up without his knowledge behind the scenes. When the inner sub is anonymous, the compiler knows that the closure must be re-resolved each time.