[Nix-dev] How are perl modules handled?

[Tobias Hunger]

Hi there!

I am having some trouble understanding how nixos handles perl module 
installations. Other scripting languages like python and ruby are most likely 
handled in a similar way.

Perl is installed in /nix/store/hasha-perl-5.10.1/...
A random perl module is installed into /nix/store/hashb-moduleB-0.8.15/...
~/.nix-profile merges those into one view of the system... which should allow 
programs using moduleB to function.

But where does moduleB document its dependency on hasha? I can't find that 
anywhere in the perl module or the sqlite DB or anywhere in /nix/var.

So how does nixos make sure that hashb is only used with the hasha version of 
perl?

Should it unlink hashb from the user environment once updating it to use 
hashc-perl-5.10.1?

How does it know the dependency on hasha?

Would something change if moduleB would contain a binary depending on 
libperl.so from hasha?

Best Regards,
Tobias