I think it will be helpful if you make certain that there's no other conf module that perl might be trying to load. Check the path of conf.pm and then run:

perl -mconf -le'print $INC{"conf.pm"}'
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If the paths don't match, then you might want to consider putting use lib "directory_of_module"; before use conf; in socket.pm to move the directory to the beginning of @INC. If the paths do match then you have a different problem. Check to make certain that you don't have a typo in the package declaration of conf.pm. For instance:

package cpnf;
#        ^-- typo, now we can't find package conf
...
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Beyond that, does the subroutine appear after an __END__ or __DATA__? Hopefully something in this rant is useful.

Update: Cleaned up and provided an example.