Erroneous module use in collection file with variable paths

[adrien-cotte]

Hello Xavier!

Describe the bug

When saving a module collection, if "module use" is applied on a path which contains a variable at the beginning, current path seems to be added just before.

To Reproduce

Steps to reproduce the behavior:

$ module use \${HOME}/modulefiles
$ module save
$ module restore
$ cat ~/.module/default
module use --append /home/cotte/${HOME}/modulefiles
...

Workaround, force "/" to obtain an absolute path:

$ module use /\${HOME}/modulefiles
$ module save
$ module restore
$ cat ~/.module/default
module use --append /${HOME}/modulefiles
...

Expected behavior

When using a variable on the first element, path must be considered as an absolute one:

$ module use \${HOME}/modulefiles
$ module save
$ module restore
$ cat ~/.module/default
module use --append ${HOME}/modulefiles
...

Modules version and configuration

$ module config
Modules Release 4.6.1 (2020-11-14)

- Config. name ---------.- Value (set by if default overridden) ---------------
advanced_version_spec     1 (env-var)
auto_handling             1 (env-var)
avail_indepth             1
avail_report_dir_sym      1
avail_report_mfile_sym    1
collection_pin_version    0
collection_target         inti (env-var)
color                     auto (env-var)
colors                    hi=1:db=2:tr=2:se=2:er=91:wa=93:me=95:in=94:mp=1;94:di=94:al=96:sy=95:de=4:cm=92
contact                   root@localhost
csh_limit                 4000
extended_default          1 (env-var)
extra_siteconfig          <undef>
home                      /usr/share/Modules (env-var)
icase                     search (env-var)
ignored_dirs              CVS RCS SCCS .svn .git .SYNC .sos
implicit_default          1
locked_configs            
ml                        1
nearly_forbidden_days     14
pager                     /usr/bin/cat (env-var)
rcfile                    <undef>
run_quarantine            LD_LIBRARY_PATH LD_PRELOAD (env-var)
search_match              starts_with
set_shell_startup         1 (env-var)
silent_shell_debug        <undef>
siteconfig                /home/cotte/modules-4.6.1/INSTALL_DIR/etc/siteconfig.tcl
tcl_ext_lib               /home/cotte/modules-4.6.1/INSTALL_DIR/lib/libtclenvmodules.so
term_background           dark
unload_match_order        returnlast
verbosity                 concise (env-var)
wa_277                    0

Thank you,
Adrien