You may want to explicitly set your path in $ENV{PATH}='/path/to/useradd'; or even better, remove everything from the %ENV hash, then explicity give the path to the useradd program in the system() call. You might want to check out the chapter on Security in Programming Perl. Also, to get a good return code from the useradd() program, you might check $? and shift it as:

$returncode=$?>>8;
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Read the perldocs on system() for further information on obtaining a good return code.

Hope that helps :-)

"Ex libris un peut de tout"