elsif(($#ARGV+1) < 1) {

##</code><code>##

elsif ($#ARGV < 0) {

##</code><code>##

elsif (@ARGV < 1) {
# or, if you prefer an explicitly stated scalar context:
elsif (scalar @ARGV < 1) {

##</code><code>##

if(! -e "$Dir") {

##</code><code>##

use strict;
use warnings;

die "Please supply an argument to the program" if @ARGV < 1;
my $dir = shift;
die "Please try again with a valid directory.\n" unless -d $dir;
# Change to user selected location
chdir $dir;
mkdir "FirstSubDir";
mkdir "SecondSubDir";