use Modern::Perl;

my $sum_of_used;

@ARGV = <C:/Users/user/Desktop/DOwork/filez/nabillingscript/09_14_2012/nas/*>;
{
    no warnings qw/numeric uninitialized/;
    $sum_of_used += (split /\s+/)[2] while <ARGV>;
}
say $sum_of_used;