Ah well ;-) GTop... this Module also has the advantage that you can query any kind of size, and you get it in bytes. Voilà:

package MemImpact::GTop;
use strict;
use GTop;

my @meths = qw(size vsize rss share);
my $before = GTop->new->proc_mem($$);
my $after = my $now = $before;

printf "%-60s % 10d Bytes\n", "$_ initial memory:" , $before->$_
    for @meths;
print "-" x 77, $/;

sub import { 
    my $pack = shift;
    my $meth = shift;
    for (@_) {
        eval "use $_;";
        die "Can't load $_:\n$@\n" if $@;
        $after = GTop->new->proc_mem($$);
        printf "%-60s % 10d Bytes\n", "$meth after loading $_:" , $aft
+er->$meth;
        printf "%-60s % 10d Bytes\n", "$meth impact of $_:" , $after->
+$meth - $now->$meth;
        $now = $after;
    }
}
END {
    print "-" x 77, $/;
    printf "%-60s % 10d Bytes\n", "$_ total impact:" , $after->$_ - $b
+efore->$_
        for @meths;
}
1;
[download]

qwurx [shmem] ~ > perl -e 'use MemImpact::GTop qw(rss Moose); use MemI
+mpact::GTop qw(rss MooseX::AttributeHelpers)'
size initial memory:                                            934707
+2 Bytes
vsize initial memory:                                           934707
+2 Bytes
rss initial memory:                                             346112
+0 Bytes
share initial memory:                                           250265
+6 Bytes
----------------------------------------------------------------------
+-------
rss after loading Moose:                                        897433
+6 Bytes
rss impact of Moose:                                            551321
+6 Bytes
rss after loading MooseX::AttributeHelpers:                    1043660
+8 Bytes
rss impact of MooseX::AttributeHelpers:                         146227
+2 Bytes
----------------------------------------------------------------------
+-------
size total impact:                                              711065
+6 Bytes
vsize total impact:                                             711065
+6 Bytes
rss total impact:                                               697548
+8 Bytes
share total impact:                                              35225
+6 Bytes
[download]