1Carp::Clan(3) User Contributed Perl Documentation Carp::Clan(3)
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6 Carp::Clan - Report errors from perspective of caller of a "clan" of
7 modules
8
10 carp - warn of errors (from perspective of caller)
11 cluck - warn of errors with stack backtrace
13 croak - die of errors (from perspective of caller)
15 confess - die of errors with stack backtrace
17 use Carp::Clan qw(^MyClan::);
19 croak "We're outta here!";
20 use Carp::Clan;
22 confess "This is how we got here!";
23
25 This module is based on ""Carp.pm"" from Perl 5.005_03. It has been
26 modified to skip all package names matching the pattern given in the
27 "use" statement inside the ""qw()"" term (or argument list).
28 Suppose you have a family of modules or classes named "Pack::A",
30 "Pack::B" and so on, and each of them uses ""Carp::Clan qw(^Pack::);""
31 (or at least the one in which the error or warning gets raised).
32 Thus when for example your script "tool.pl" calls module "Pack::A", and
34 module "Pack::A" calls module "Pack::B", an exception raised in module
35 "Pack::B" will appear to have originated in "tool.pl" where "Pack::A"
36 was called, and not in "Pack::A" where "Pack::B" was called, as the
37 unmodified ""Carp.pm"" would try to make you believe ":-)".
38 This works similarly if "Pack::B" calls "Pack::C" where the exception
40 is raised, etcetera.
41 In other words, this blames all errors in the ""Pack::*"" modules on
43 the user of these modules, i.e., on you. ";-)"
44 The skipping of a clan (or family) of packages according to a pattern
46 describing its members is necessary in cases where these modules are
47 not classes derived from each other (and thus when examining @ISA - as
48 in the original ""Carp.pm"" module - doesn't help).
49 The purpose and advantage of this is that a "clan" of modules can work
51 together (and call each other) and throw exceptions at various depths
52 down the calling hierarchy and still appear as a monolithic block (as
53 though they were a single module) from the perspective of the caller.
54 In case you just want to ward off all error messages from the module in
56 which you ""use Carp::Clan"", i.e., if you want to make all error mes‐
57 sages or warnings to appear to originate from where your module was
58 called (this is what you usually used to ""use Carp;"" for ";-)"),
59 instead of in your module itself (which is what you can do with a "die"
60 or "warn" anyway), you do not need to provide a pattern, the module
61 will automatically provide the correct one for you.
62 I.e., just ""use Carp::Clan;"" without any arguments and call "carp" or
64 "croak" as appropriate, and they will automatically defend your module
65 against all blames!
66 In other words, a pattern is only necessary if you want to make several
68 modules (more than one) work together and appear as though they were
69 only one.
70 Forcing a Stack Trace
72 As a debugging aid, you can force ""Carp::Clan"" to treat a "croak" as
74 a "confess" and a "carp" as a "cluck". In other words, force a detailed
75 stack trace to be given. This can be very helpful when trying to under‐
76 stand why, or from where, a warning or error is being generated.
77 This feature is enabled either by "importing" the non-existent symbol
79 'verbose', or by setting the global variable "$Carp::Clan::Verbose" to
80 a true value.
81 You would typically enable it by saying
83 use Carp::Clan qw(verbose);
85 Note that you can both specify a "family pattern" and the string "ver‐
87 bose" inside the ""qw()"" term (or argument list) of the "use" state‐
88 ment, but consider that a pattern of packages to skip is pointless when
89 "verbose" causes a full stack trace anyway.
90
92 The ""Carp::Clan"" routines don't handle exception objects currently.
93 If called with a first argument that is a reference, they simply call
94 ""die()"" or ""warn()"", as appropriate.
95perl v5.8.8 2006-10-02 Carp::Clan(3)