1Carp::Clan(3) User Contributed Perl Documentation Carp::Clan(3)
2
6 Carp::Clan - Report errors from perspective of caller of a "clan" of
7 modules
8
10 version 6.08
11
13 carp - warn of errors (from perspective of caller)
14 cluck - warn of errors with stack backtrace
16 croak - die of errors (from perspective of caller)
18 confess - die of errors with stack backtrace
20 use Carp::Clan qw(^MyClan::);
22 croak "We're outta here!";
23 use Carp::Clan;
25 confess "This is how we got here!";
26
28 This module is based on ""Carp.pm"" from Perl 5.005_03. It has been
29 modified to skip all package names matching the pattern given in the
30 "use" statement inside the ""qw()"" term (or argument list).
31 Suppose you have a family of modules or classes named "Pack::A",
33 "Pack::B" and so on, and each of them uses ""Carp::Clan qw(^Pack::);""
34 (or at least the one in which the error or warning gets raised).
35 Thus when for example your script "tool.pl" calls module "Pack::A", and
37 module "Pack::A" calls module "Pack::B", an exception raised in module
38 "Pack::B" will appear to have originated in "tool.pl" where "Pack::A"
39 was called, and not in "Pack::A" where "Pack::B" was called, as the
40 unmodified ""Carp.pm"" would try to make you believe ":-)".
41 This works similarly if "Pack::B" calls "Pack::C" where the exception
43 is raised, et cetera.
44 In other words, this blames all errors in the ""Pack::*"" modules on
46 the user of these modules, i.e., on you. ";-)"
47 The skipping of a clan (or family) of packages according to a pattern
49 describing its members is necessary in cases where these modules are
50 not classes derived from each other (and thus when examining @ISA - as
51 in the original ""Carp.pm"" module - doesn't help).
52 The purpose and advantage of this is that a "clan" of modules can work
54 together (and call each other) and throw exceptions at various depths
55 down the calling hierarchy and still appear as a monolithic block (as
56 though they were a single module) from the perspective of the caller.
57 In case you just want to ward off all error messages from the module in
59 which you ""use Carp::Clan"", i.e., if you want to make all error
60 messages or warnings to appear to originate from where your module was
61 called (this is what you usually used to ""use Carp;"" for ";-)"),
62 instead of in your module itself (which is what you can do with a "die"
63 or "warn" anyway), you do not need to provide a pattern, the module
64 will automatically provide the correct one for you.
65 I.e., just ""use Carp::Clan;"" without any arguments and call "carp" or
67 "croak" as appropriate, and they will automatically defend your module
68 against all blames!
69 In other words, a pattern is only necessary if you want to make several
71 modules (more than one) work together and appear as though they were
72 only one.
73 Forcing a Stack Trace
75 As a debugging aid, you can force ""Carp::Clan"" to treat a "croak" as
76 a "confess" and a "carp" as a "cluck". In other words, force a detailed
77 stack trace to be given. This can be very helpful when trying to
78 understand why, or from where, a warning or error is being generated.
79 This feature is enabled either by "importing" the non-existent symbol
81 'verbose', or by setting the global variable "$Carp::Clan::Verbose" to
82 a true value.
83 You would typically enable it by saying
85 use Carp::Clan qw(verbose);
87 Note that you can both specify a "family pattern" and the string
89 "verbose" inside the ""qw()"" term (or argument list) of the "use"
90 statement, but consider that a pattern of packages to skip is pointless
91 when "verbose" causes a full stack trace anyway.
92
94 The ""Carp::Clan"" routines don't handle exception objects currently.
95 If called with a first argument that is a reference, they simply call
96 ""die()"" or ""warn()"", as appropriate.
97 Bugs may be submitted through the RT bug tracker
99 <https://rt.cpan.org/Public/Dist/Display.html?Name=Carp-Clan> (or
100 bug-Carp-Clan@rt.cpan.org <mailto:bug-Carp-Clan@rt.cpan.org>).
101
103 Steffen Beyer <STBEY@cpan.org>
104
106 • Karen Etheridge <ether@cpan.org>
107 • Joshua ben Jore <jjore@cpan.org>
109 • Kent Fredric <kentnl@cpan.org>
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113 This software is copyright (c) 2001 by Steffen Beyer, Joshua ben Jore.
114 This is free software; you can redistribute it and/or modify it under
116 the same terms as the Perl 5 programming language system itself.
117perl v5.36.0 2022-07-22 Carp::Clan(3)