my $in1 = $ARGV[0];
chomp(my $in2 = $ARGV[1] // '');

if (defined $in1) {
   $in1 =~ s/\s+//g; # Remove all whitespace instead of chomp
   if ($in1 =~ /\D+/) {
      print "Input invalid. Only numbers are allowed\n";
   }
} else {
   print "No valid input given\n";
}