Hi,

But the "or die" part is wrong: system() will return the exit status of the process, which is based on shell semantics: a return value of zero means "success" (i.e. "good") whereas any non-zero value means "failure" (i.e. "bad") -- so you probably want to say "and die" instead.

You are wrong, the example is fine.

system('procheck', $pdbfile, '1.0') == 0 or die "system failed ( $? )"
+;
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die is only called, if the returncode from system is not 0. This is exactly what we want it to do.