Perl - Subroutine redefined

Question

I have asked this question before or searched and seen others ask - why am I getting the warning \"Subroutine mySub redefined at ../lib/Common.pm line x\"? and you

Answer 1

This sounds like a problem caused by circular dependencies. Here is how to track it down. If your problem class looks like this:

package AlientPlanet;
use Dinosaurs;
sub has_dinosaurs {...}
1;

Then change your example to look like this:

package AlienPlanet;
sub has_dinosaurs {...}     # <-- swap
use Dinosaurs;              # <-- swap
1;

Now compile your code with Carp::Always like this:

⚡ perl -MCarp::Always -c lib/AlienPlanet.pm                                                                                                            
Subroutine has_dinosaurs redefined at lib/AlienPlanet.pm line 4.
    require AlienPlanet.pm called at lib/Dinosaurs.pm line 4
    Dinosaurs::BEGIN() called at lib/AlienPlanet.pm line 4
    eval {...} called at lib/AlienPlanet.pm line 4
    require Dinosaurs.pm called at lib/AlienPlanet.pm line 5
    AlienPlanet::BEGIN() called at lib/AlienPlanet.pm line 4
    eval {...} called at lib/AlienPlanet.pm line 4
lib/AlienPlanet.pm syntax OK

Now that you have a stacktrace you can see where the loop is. The quick and dirty solution is to use Class::Load in Dinosaurs.pm.

For a more detailed explanation try my blog post.