From perldoc -f system:

The return value is the exit status of the program as
returned by the "wait" call.  To get the actual exit
value shift right by eight (see below).  See also "exec".

[snip]

You can check all the failure possibilities by inspecting $?
like this:

   $exit_value  = $? >> 8;
   $signal_num  = $? & 127;
   $dumped_core = $? & 128;

or more portably by using the W*() calls of the POSIX exten-
sion; see perlport for more information.
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