sub format_kilo  # Kilo, mega and gig
{
    my $number = shift;
    my $fixwidth = shift;
    my $suffix = " ";

    if ($number > 0x40000000)
    {
        $number /= 0x40000000;
        $suffix = 'G';
    }
    elsif ($number > 0x100000)
    {
        $number /= 0x100000;
        $suffix = 'M';
    }
    elsif ($number > 0x400)
    {
        $number /= 0x400;
        $suffix = 'K';
    }

    # Split integer and decimal parts of the number and add commas
    my $integer = int($number);

    # Add Leading spaces if fixed width
    $fixwidth and $integer =  ' ' x ($fixwidth - length($integer) - length($suffix)) . $integer;

    # Combine it all back together and return it.
    return $integer.$suffix;
}

##### Calling sequence ###
my ($filename, $filebytes);
$filename = "Your file name here....";
$filebytes = -s $filename;

print "Opening File=$filename; (".
    format_kilo($filebytes)  . " [=$filebytes] bytes)\n";