Module unload command does not work from within a module file

Issue

• module unload command does not work from within a module file.
• The complete reproducer:

[root@localhost test]# cat first 
#%Module

append-path PATH /home

[root@localhost test]# cat second 
#%Module

module unload first                                    --> This line will unload the  module named "first"

[root@localhost test]# module list
No Modulefiles Currently Loaded.

[root@localhost test]# module load /home/test/first    --> This will load module named "first"

[root@localhost test]# module list                     -->  module named "first" is loaded
Currently Loaded Modulefiles:
  1) /home/test/first

[root@localhost test]# module load /home/test/second   --> This will load module named "second"

[root@localhost test]# module list                     --> both modules are loaded.
                                                           Here module named "first" should
                                                           have been unloaded since the module
                                                           named "second" contains a line which
                                                           will unload the module named "first" )
Currently Loaded Modulefiles:
  1) /home/test/first    2) /home/test/second