We are all used to checking $! in error messages after failed system calls. However when you reap a child you may know the return code (it is in $?), but would still like to get the system message. For instance the return is 2 and you would like to see No such file or directory. How can you get the translation?

The secret involves some deep magic of $! that is documented in perlvar. It is different when being treated as a string and a number. You can assign the numerical return code, and when used as a string it will have the text of the message. (If the return is being used as a string, there is no need to coerce it like I did. But enough magic is going on that I *prefer* doing that.)

# Turns numerical return codes into text.  See perlvar.
sub get_system_error {
  local $! = shift;
  return "$!";
}

print "$_: ", get_system_error($_), "\n" foreach 1..50;
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