I have started working with pathogen.vim with gvim on Windows, following Tim Pope's setup guide at his github repository here.

However, I'm running into the problem that pathogen#infect() does not seem to be modifying the runtimepath (as seen by running :echo &runtimepath in gvim).

The simple test case _vimrc that I came up with is as follows. Please note that pathogen gets loaded just fine.

"Set a base directory.
let $BASE_DIR='H:\development\github\vimrc'

"Source pathogen since it's not in the normal autoload directory.
source $BASE_DIR\autoload\pathogen.vim

"Start up pathogen
call pathogen#infect()
"call pathogen#infect('$BASE_DIR\functions')

Neither running pathogen#infect() without an argument (which should add the bundles directory under the vimfiles directory) nor specifying a directory to contain files works.

Substituting the pathogen#infect() call with pathogen#runtime_prepend_subdirectories('$BASE_DIR\functions'), which is what pathogen#infect() does fails to change the runtimepath as well.

Any ideas that I've missed? Any more information that would be helpful?

My repository with the non-trivial example is here.