What does "redefining module" error in erlang mean?

I added the mochijson2.erl module to my ejabberd src directory but when I try to compile the code I get the following error:

 ./mochijson2.erl:8: redefining module

Where could this module be defined? I don't have it in my sour开发者_如何学运维ce.

It means your module has two -module(...) directives, which is not allowed. Check the source code of the module.