Special Variable Access

byrned has asked for the wisdom of the Perl Monks concerning the following question:

The question is simple, but I suspect the answer may not be. I want to set $! to generate custom error messages from my packages and objects. I know this is possible with a Perl extension written in C, but I don’t want to do that. The main goal is to use a truly global variable to pass error data in. Right now I’m using $_, but I have to be careful to avoid other functions from overwriting it. Thanks.

Comment on Special Variable Access

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Re: Special Variable Access by BazB (Priest) on Jan 25, 2003 at 00:40 UTC
Is over-writing `$!` a good idea? The errno values that pfaut(++) mentions are there for a reason. What is wrong with supplying your error message to `die` (or `warn`, or any of the Carp methods) in the normal way: `die "Custom error messages are good!" if $condition;` [download] You don't have to include `$!` in your die statements, if you don't want to. Alternatively, you can install a `__DIE__` handler to override the default behaviour of die: `#!/usr/bin/perl use strict; use warnings; local $SIG{__DIE__} = sub { die scalar localtime(), " " , $_[0] }; die "Argh!";` [download] produces: `Sat Jan 25 00:40:36 2003 Argh! at ./custom_die.pl line 8.` [download] If the information in this post is inaccurate, or just plain wrong, don't just downvote - please post explaining what's wrong. That way everyone learns.	[reply] [d/l] [select]
Re: Special Variable Access by pfaut (Priest) on Jan 25, 2003 at 00:32 UTC
If the errors you are returning can be expressed as errno values, just assign the numeric value to $!. Things should work as expected. If you want to set error strings, try using $@ which is used by eval. Some CPAN modules (IO::Socket::INET for one) also use it to return error strings. `--- print map { my ($m)=1<<hex($_)&11?' ':''; $m.=substr('AHJPacehklnorstu',hex($_),1) } split //,'2fde0abe76c36c914586c';` [download]	[reply] [d/l]