if ($number =~ /[-.]+/)
 if ($number =~ /\D/)
into just one regex: if( $number =~/[-.\D]/)
    {
       print "Invalid!! Only unsigned integer numbers >=0 are allowed!\n";
       next;
    }
probably could add if( $number =~/[-.+\D]/) also to disallow the + sign.
But I don't this minor issue detracts from the main point.