system returns the status of the command returned by wait. Typical unix commands and C functions return '0' on success (ie, there was no error)

See the following example:

$ perl -e '$var = system("true"); print "[$var]\n"'
[0]
$ perl -e '$var = system("false"); print "[$var]\n"'
[256]
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Update: oops... shift 8 places to get the status of the command. 'false' should have returned '1':

$ false; echo $?
1
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