General convention to indicate whether a program has exited successfully or not is the exit status of the program. If the exit status is equal to 0 then it was successful, otherwise a failure e.g

system("some_program --and arguments") == 0
  or die("Couldn't do something with stuff");
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Although in your case it looks like mkdir would be the better option. See. system for more info on the exit status of programs (which lives in the $? variable).
HTH

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broquaint