osx man page for errno

Errno(3pm)						 Perl Programmers Reference Guide						Errno(3pm)

NAME
       Errno - System errno constants

SYNOPSIS
	   use Errno qw(EINTR EIO :POSIX);

DESCRIPTION
       "Errno" defines and conditionally exports all the error constants defined in your system "errno.h" include file. It has a single export
       tag, ":POSIX", which will export all POSIX defined error numbers.

       "Errno" also makes "%!" magic such that each element of "%!" has a non-zero value only if $! is set to that value. For example:

	   use Errno;

	   unless (open(FH, "/fangorn/spouse")) {
	       if ($!{ENOENT}) {
		   warn "Get a wife!
";
	       } else {
		   warn "This path is barred: $!";
	       }
	   }

       If a specified constant "EFOO" does not exist on the system, $!{EFOO} returns "".  You may use "exists $!{EFOO}" to check whether the
       constant is available on the system.

CAVEATS
       Importing a particular constant may not be very portable, because the import will fail on platforms that do not have that constant.  A more
       portable way to set $! to a valid value is to use:

	   if (exists &Errno::EFOO) {
	       $! = &Errno::EFOO;
	   }

AUTHOR
       Graham Barr <gbarr@pobox.com>

COPYRIGHT
       Copyright (c) 1997-8 Graham Barr. All rights reserved.  This program is free software; you can redistribute it and/or modify it under the
       same terms as Perl itself.

perl v5.16.2							    2013-08-25								Errno(3pm)