use strict;
use warnings;
use Archive::Tar;

die "no file?" unless $ARGV[0] and -f $ARGV[0];

my $size = 0;
my @arch = Archive::Tar->new($ARGV[0])->list_files([qw(size)]);

$size += $_->{size} for @arch;

eval "use Number::Format";
if( $@ ) {
    print "$size\n";

} else {
    my $fmt = new Number::Format;
    print "", $fmt->format_bytes( $size, 1), "\n";
}