In addition to what Anonymous Monk said, I would comment that this conditional statement:

elsif(($#ARGV+1) < 1) {
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elsif ($#ARGV < 0) {
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Second, if you want to test the number of arguments passed to the program, it is clearer to evaluate @ARGV in scalar context (which gives the number of items in that array):

elsif (@ARGV < 1) {
# or, if you prefer an explicitly stated scalar context:
elsif (scalar @ARGV < 1) {
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if(! -e "$Dir") {
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So if you want to check that at least one argument is being passed to the program, you should do it first.

Also, it is a bit useless to check for the existence of $Dir and then whether it is a valid directory (unless you want to print a different message in that case); you can check directly that it is a valid directory.

So, this program could be rewritten as:

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";
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In keeping with your recommended best practices of error checking at each step, the main code should be

chdir $dir           or die "ERROR: Could not change directory to $dir
+";
mkdir "FirstSubDir"  or die "ERROR creating FirstSubdir:$!";
mkdir "SecondSubDir" or die "ERROR creating SecondSubDir:$!";
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                All power corrupts, but we need electricity.

of course once we get into checking the returns, we may find chdir does all the testing we need already ...

use strict;
use warnings;
use Cwd;
my $dir = shift;
chdir $dir or die "Couldn't chdir $dir: $!\n";
print "OK, in ". getcwd . "\n";
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And the outut

# ./change.pl Downloads/
OK, in /home/Random/Downloads
# ./perl change.pl foo
Couldn't chdir foo: No such file or directory
# ./mkdir bar
# ./chmod 000 bar
# ./perl change.pl bar
Couldn't chdir bar: Permission denied
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Cheers,
R.

Pereant, qui ante nos nostra dixerunt!

Yes, agreed ++. Here, I wanted to keep it simple in the context of an exercise.

Although, to tell the full truth, I am not sure I would really check the chdir return status after I have checked that $dir contains a valid directory entry in the current directory (I know it might still fail for various reasons, such as missing privileges, but this is quite unlikely in my context and, sometimes, there is a trade-off between code complexity and coding efficiency). Or I might probably use the autodie module in such a context with a lot of system calls.

Update: or, as suggested by Random_Walk, we might go the other way around and let chdir do the checks.

Hi,

You've forgotten to mkdir the directories.

Also, always, always, always use strict and warnings, always, get in the habit now, it will save you much time and trouble in the future.

Also, always etc. check return values, it will save etc.

J.C.

I know I didn't create any. Right now, my script won't change into the directory given as an argument. For example, inside my ubuntu terminal I created a directory called test. then I tried to run the script with "test" as an argument. I expected to then be inside of test. Nothing happened.

Any changes to what is the current directory made while running perl disapear when perl ends.

in your perl script add

    use Cwd;
    print 'Cwd:'.getcwd."\n";
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after the

chdir($Dir);
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and you will see that you did move to that directory while perl was running.