The Perl system command gives the return code of the process call in the upper byte of a two byte word. Right shifting this code 8 bits will give you the return code of the operation.

 
  ... # some code

  print "Importing $FILE.\n";

  $rtncd = system("mysql < $FILE") >> 8; # shift right 8 bits to recov
+er actual code 
  if($rtncd == 0){
      ...  # everything OK
  }else{
      ...  # some problem ?
  }

  print "Sleeping for 5.\n";
  system('sleep 5');

  ... #more coce
[download]

If you want to capture the output of the mysql call, use backticks or qx// such as $rtncd = `mysql < $FILE`;. Often, when the actual program return code isn't helpful (for example my program fails gracefully which annoyingly produces a clean return code of 0) I have the program print an error message or error code and then capture that output via backticks. It works pretty well.