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Carp::Clan(3pm) User Contributed Perl Documentation Carp::Clan(3pm)
NAME
Carp::Clan - Report errors from perspective of caller of a "clan" of modules
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 AT rt.org <mailto:bug-Carp-Clan AT rt.org>).
AUTHOR
Steffen Beyer <STBEY AT cpan.org>
CONTRIBUTORS
o Karen Etheridge <ether AT cpan.org>
o Joshua ben Jore <jjore AT cpan.org>
o Kent Fredric <kentnl AT 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.
perl v5.30.0 2019-10-13 Carp::Clan(3pm)
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