Why should I use Carp instead of warn in Perl?

Question

People keep giving me examples with carp instead of warn. Why? What makes carp better than warn?

Answer 1

carp gives you more info as to where the message comes from (context)

#!/usr/bin/perl  use Carp;  foo(); bar(); baz();  sub foo {   warn "foo"; }  sub bar {   carp "bar"; }  sub baz {   foo();   bar();  } 

produces

foo at ./foo.pl line 9. bar at ./foo.pl line 13         main::bar() called at ./foo.pl line 6 foo at ./foo.pl line 10. bar at ./foo.pl line 14         main::bar() called at ./foo.pl line 19         main::baz() called at ./foo.pl line 7 

kinda silly for this small program but comes in handy when you want to know who called the method that's carp'ing.

Answer 2

I use warn for scripts and simple programs, and Carp inside any modules. The Carp subroutines use the filename and line number where your current subroutine was called so it's easier to find who's causing the problem (not just where the problem manifested itself).

Damian recommends Carp instead of warn in "Reporting Failure" in Perl Best Practices, but doesn't make the distinction between scripts as top-level code constructs and modules as components that programs use.

I've mostly not cared about that lately because I've been using Log::Log4perl to handle all of that.