You might want to consider using $SIG{__DIE__} instead of the FatalError subroutine. Put what you are doing in the FatalError into the subroutine for the DIE signal handler, evaluate $? (instead of $!) before die'ing.

Something like:

$SIG{__DIE__}=sub{
                  print STDERR "I'm Dyin!: \n";
                 };

some_command;
$error_code=$?>>8;
print "Finished running some_command";
die if $error_code > 0;
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