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=head1 NAME
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Carp::Clan - Report errors from perspective of caller of a "clan" of modules
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=head1 SYNOPSIS
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carp - warn of errors (from perspective of caller)
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cluck - warn of errors with stack backtrace
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croak - die of errors (from perspective of caller)
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confess - die of errors with stack backtrace
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use Carp::Clan qw(^MyClan::);
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croak "We're outta here!";
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use Carp::Clan;
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confess "This is how we got here!";
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=head1 DESCRIPTION
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This module is based on "C<Carp.pm>" from Perl 5.005_03. It has been
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modified to skip all package names matching the pattern given in
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the "use" statement inside the "C<qw()>" term (or argument list).
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Suppose you have a family of modules or classes named "Pack::A",
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"Pack::B" and so on, and each of them uses "C<Carp::Clan qw(^Pack::);>"
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(or at least the one in which the error or warning gets raised).
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Thus when for example your script "tool.pl" calls module "Pack::A",
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and module "Pack::A" calls module "Pack::B", an exception raised in
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module "Pack::B" will appear to have originated in "tool.pl" where
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"Pack::A" was called, and not in "Pack::A" where "Pack::B" was called,
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as the unmodified "C<Carp.pm>" would try to make you believe C<:-)>.
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This works similarly if "Pack::B" calls "Pack::C" where the
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exception is raised, etcetera.
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In other words, this blames all errors in the "C<Pack::*>" modules
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on the user of these modules, i.e., on you. C<;-)>
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The skipping of a clan (or family) of packages according to a pattern
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describing its members is necessary in cases where these modules are
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not classes derived from each other (and thus when examining C<@ISA>
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- as in the original "C<Carp.pm>" module - doesn't help).
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The purpose and advantage of this is that a "clan" of modules can work
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together (and call each other) and throw exceptions at various depths
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down the calling hierarchy and still appear as a monolithic block (as
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though they were a single module) from the perspective of the caller.
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In case you just want to ward off all error messages from the module
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in which you "C<use Carp::Clan>", i.e., if you want to make all error
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messages or warnings to appear to originate from where your module
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was called (this is what you usually used to "C<use Carp;>" for C<;-)>),
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instead of in your module itself (which is what you can do with a
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"die" or "warn" anyway), you do not need to provide a pattern,
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the module will automatically provide the correct one for you.
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I.e., just "C<use Carp::Clan;>" without any arguments and call "carp"
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or "croak" as appropriate, and they will automatically defend your
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module against all blames!
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In other words, a pattern is only necessary if you want to make
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several modules (more than one) work together and appear as though
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they were only one.
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=head2 Forcing a Stack Trace
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As a debugging aid, you can force "C<Carp::Clan>" to treat a "croak" as
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a "confess" and a "carp" as a "cluck". In other words, force a detailed
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stack trace to be given. This can be very helpful when trying to
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understand why, or from where, a warning or error is being generated.
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This feature is enabled either by "importing" the non-existent symbol
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'verbose', or by setting the global variable "C<$Carp::Clan::Verbose>"
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to a true value.
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You would typically enable it by saying
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use Carp::Clan qw(verbose);
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Note that you can both specify a "family pattern" and the string "verbose"
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inside the "C<qw()>" term (or argument list) of the "use" statement, but
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consider that a pattern of packages to skip is pointless when "verbose"
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causes a full stack trace anyway.
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=head1 BUGS
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The "C<Carp::Clan>" routines don't handle exception objects currently.
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If called with a first argument that is a reference, they simply
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call "C<die()>" or "C<warn()>", as appropriate.
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