[Modules] `module use --append` and `append-path MODULEPATH` replace centrally set MODULEPATH instead of appending to it

[Frank T. <f.t...@dk...>]

Hi,

this is most probably a silly error on my side, but I haven't found the 
solution: When having a custom ~/.modulerc with

   #%Module
   module use --append /a/b/c
   append-path MODULEPATH /d/e/f

the resulting $MODULEPATH is "/a/b/c:/d/e/f".  I would have expected it 
to be "$CENTRALLY_SET_MODULEPATHS:/a/b/c:/d/e/f".  When only using 
`append-path` it looks similar:

   #%Module
   append-path MODULEPATH /d/e/f

results in $MODULEPATH being "/d/e/f" instead of 
"$CENTRALLY_SET_MODULEPATHS:/d/e/f".

This is with Modules 5.0.1 on CentOS 7.9 systems. We have not changed 
any of the other configuration files after the installation other than 
populating etc/modulespath with our central modulefile repository pathes.

What have I overlooked?

Cheers, Frank