carp - warn of errors (from perspective of caller)
cluck - warn of errors with stack backtrace (not exported by default)
croak - die of errors (from perspective of caller)
confess - die of errors with stack backtrace
use Carp; croak "We're outta here!"; use Carp qw(cluck); cluck "This is how we got here!";
The Carp routines are useful in your own modules because they act like die() or warn(), but report where the error was in the code they were called from. Thus if you have a routine Foo() that has a carp() in it, then the carp() will report the error as occurring where Foo() was called, not where carp() was called.
As a debugging aid, you can force Carp to treat a croak as a confess and a carp as a cluck across all modules. 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 by 'importing' the non-existent symbol 'verbose'. You would typically enable it by saying
perl -MCarp=verbose script.pl
or by including the string
MCarp=verbose in the PERL5OPT environment variable.