info > Carp::Clan

📝 NAME

Carp::Clan - Report errors from perspective of caller of a "clan" of modules

🚀 Quick Reference

Use Case	Command	Description
🔴 Warn from caller perspective	carp "message"	Warn as if error originated at caller
🔴 Die from caller perspective	croak "message"	Die as if error originated at caller
🔍 Stack trace on warn	cluck "message"	Warn with full stack backtrace
🔍 Stack trace on die	confess "message"	Die with full stack backtrace
🏢 Create a module clan	use Carp::Clan qw(^MyClan::)	Skip all packages matching pattern in error reports
🔧 Force verbose trace	use Carp::Clan qw(verbose)	Treat croak as confess, carp as cluck

📦 VERSION

version 6.08

📋 SYNOPSIS

• carp - warn of errors (from perspective of caller)
• cluck - warn of errors with stack backtrace
• croak - die of errors (from perspective of caller)
• confess - die of errors with stack backtrace

   use Carp::Clan qw(^MyClan::);
   croak "We're outta here!";

   use Carp::Clan;
   confess "This is how we got here!";

📖 DESCRIPTION

This module is based on Carp.pm from Perl 5.005_03. It has been modified to skip all package names matching the pattern given in the use statement inside the qw() term (or argument list).

Suppose you have a family of modules or classes named Pack::A, Pack::B and so on, and each of them uses Carp::Clan qw(^Pack::) (or at least the one in which the error or warning gets raised).

Thus when for example your script tool.pl calls module Pack::A, and module Pack::A calls module Pack::B, an exception raised in module Pack::B will appear to have originated in tool.pl where Pack::A was called, and not in Pack::A where Pack::B was called, as the unmodified Carp.pm would try to make you believe 😊.

This works similarly if Pack::B calls Pack::C where the exception is raised, et cetera.

In other words, this blames all errors in the Pack::* modules on the user of these modules, i.e., on you. 😉

The skipping of a clan (or family) of packages according to a pattern describing its members is necessary in cases where these modules are not classes derived from each other (and thus when examining @ISA - as in the original Carp.pm module - doesn't help).

The purpose and advantage of this is that a "clan" of modules can work together (and call each other) and throw exceptions at various depths down the calling hierarchy and still appear as a monolithic block (as though they were a single module) from the perspective of the caller.

In case you just want to ward off all error messages from the module in which you use Carp::Clan, i.e., if you want to make all error messages or warnings to appear to originate from where your module was called (this is what you usually used to use Carp for 😊), instead of in your module itself (which is what you can do with a die or warn anyway), you do not need to provide a pattern, the module will automatically provide the correct one for you.

I.e., just use Carp::Clan without any arguments and call carp or croak as appropriate, and they will automatically defend your module against all blames!

In other words, a pattern is only necessary if you want to make several modules (more than one) work together and appear as though they were only one.

🔍 Forcing a Stack Trace

As a debugging aid, you can force Carp::Clan to treat a croak as a confess and a carp as a cluck. In other words, force a detailed stack trace to be given. This can be very helpful when trying to understand why, or from where, a warning or error is being generated.

This feature is enabled either by "importing" the non-existent symbol 'verbose', or by setting the global variable $Carp::Clan::Verbose to a true value.

You would typically enable it by saying

   use Carp::Clan qw(verbose);

Note that you can both specify a "family pattern" and the string "verbose" inside the qw() term (or argument list) of the use statement, but consider that a pattern of packages to skip is pointless when "verbose" causes a full stack trace anyway.

🐛 BUGS

The Carp::Clan routines don't handle exception objects currently. If called with a first argument that is a reference, they simply call die() or warn(), as appropriate.

Bugs may be submitted through the RT bug tracker <https://rt.cpan.org/Public/Dist/Display.html?Name=Carp-Clan> (or bug-Carp-Clan@rt.org <mailto:bug-Carp-Clan@rt.org>).

👤 AUTHOR

Steffen Beyer <STBEY@cpan.org>

👥 CONTRIBUTORS

• Karen Etheridge <ether@cpan.org>
• Joshua ben Jore <jjore@cpan.org>
• Kent Fredric <kentnl@cpan.org>

📄 COPYRIGHT AND LICENSE

This software is copyright (c) 2001 by Steffen Beyer, Joshua ben Jore.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.