> I would like to know the module names I have declared in other file
> but I don't know how to do it.

From=20
$ ri Module.constants

(from ruby core)
---------------------------------------------------------------------------=
---
  Module.constants   -> array

---------------------------------------------------------------------------=
---

Returns an array of the names of all constants defined in the system.
This list includes the names of all modules and classes.

Also, I discovered this for myself in about 1 minute with irb, by
doing this:

irb(main):001:0> module A
irb(main):002:1> module B
irb(main):003:2> end
irb(main):004:1> end
=3D> nil
irb(main):005:0> A.methods.sort
=3D>
...here I looked at the list of methods...
irb(main):006:0> A.constants
=3D> [:B]

Wishing you happy learnings,

Johnny