Why does swapping module with '--delim' option is broken in environment-modules ?

Issue

Swapping of module with --delim option is broken in environment-modules 3.2.9.

See the following reproducer:

1. $ export MODULEPATH=~/modules/module/
2. $ cat ~/modules/module/module1
#%Module
append-path -d " " testpath "-I/mpidir1"

3. $ cat ~/modules/module/module2
#%Module
append-path -d " " testpath "-I/mpidir2"

4. $ module load module1
5. $ echo $testpath
6. $ module switch module1 module2
7. $ echo $testpath
8. $ module unload module2
9. $ echo $testpath

Actual results:

5.
-I/mpidir1
7.
I/mpidir2
9.
I/mpidir2


Expected results:

5.
-I/mpidir1
7.
-I/mpidir2
9.
<empty>