#!/usr/bin/perl -l

use strict;
use warnings;
use File::Find;

my $size = 0;
find( sub {
    $size += -f $_ ? -s _ : 0 }, shift(@ARGV));
$size = sprintf( "%.02f", $size / 1024 / 1024);
print "$size MB";

__END__
returned: 110.11 MB for /etc