perldoc > 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
    *   Karen Etheridge <ether AT cpan.org>

    *   Joshua ben Jore <jjore AT cpan.org>

    *   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.