Let's decode the return value:
perl -e'print 65288 >> 8, $/' prints 255, or as hotshot said, -1 which is usually a nonspecific error return.
perl -e'print 65288 & 128, $/' prints 0, so core was not dumped.
perl -e'print 65288 & 127, $/' prints 8, so the system call was ended with a signal. Signal 8 on my system is an FPU exception, unsurprising in an encryption program.

Update: Oops. Misread the return, 65280 & 127 is 0, no signal involved.

After Compline,
Zaxo