use strict;
use Devel::Size qw(size total_size);

sub mem_size {
  my($pkg, $type) = @_;

  die("mem_size(): unknown variable type '$type'\n")
    if $type !~ /^(?: HASH | ARRAY | SCALAR )\z/x;

  my $ret = 0;
  no strict 'refs';
  for(values %{"${pkg}::"}) {
    $ret += ( $type eq 'SCALAR' ?
                size( ${ *$_{$type} } ) :
                total_size( *$_{$type} ) )
      if defined *$_{$type};
  }
  return $ret;
}

print "SCALAR mem usage in main:: is ",
      mem_size("main", "SCALAR"), $/;

__output__

SCALAR mem usage in main:: is 2098