What was the error message,"Invalid argument" ?. Try adding chomp

#!perl
use strict;
use warnings;

my $cwd = 'C:/Users/darkblack/Desktop';

print "Enter directory name > ";
chomp(my $dir = <STDIN>);
$dir = "$cwd/$dir";

mkdir( $dir , 0755 ) or die "Could not create $dir : $!";
print "Directory $dir created successfully\n";
[download]