I've tried: print `cd desktop`; print `mkdir robert`;

OK: why are you trying to print values from a shell command that isn't going to write anything to STDOUT/STDERR?

As belg4mit pointed out what you really want to use are the built-in functions. Examples:

  :
  :
  :
mkdir $some_dir;
chdir $some_dir; 
  :
  :
[download]

Now, what I've shown above is a very basic way of using those built-ins. You can also trap some errors from these built-ins as well. For instance:

 |
 |
chdir $some_dir or die "HEY!  I couldn't CD into $some_dir:$!";
  |
  |
mkdir $another_dir or die "OHMIGOD! I couldn't make $another_dir:$!"; 
   |
   |
[download]

Now, it must be noted that under *nix the value of umask is going to influence the behavior of mkdir and what the resultant permissions of the created directory are. But that, kind monk I leave as an excersise in your own ability to learn more about.