Add suffix to file with context menu in Windows Explorer

Want to add a suffix to (rename) filenames via right click menu.

Like this:

1. Right click on file.
2. Select the suffix from context menu.
3. The file gets renamed.

I tried adding the following registry entry:

HKEY_CLASSES_ROOT
  *
    shell
      old
        command
          cmd /c ren "%1" "%1 old"

But it results in syntax error.

Would be awesome if it could be used to select and rename multiple files at once.

==> ren /?
Renames a file or files.

RENAME [drive:][path]filename1 filename2.
REN [drive:][path]filename1 filename2.

Note that you cannot specify a new drive or path for your destination file.

==> reg query "HKEY_CLASSES_ROOT\*\shell\Old\command"

HKEY_CLASSES_ROOT\*\shell\Old\command
    (Default)    REG_SZ    cmd /C for %%# in ("%1") do  ren "%~f#" "%~n# old%~x#"

Above registry setting leads to e.g. ren "D:\tmp\dummy foo.txt" "dummy foo old.txt".

And yes, it could be used to select multiple files at once. Invokes a distinct cmd instance for every selected file.

Resources (required reading):

• (command reference) An A-Z Index of the Windows CMD command line
• (helpful particularities) Windows CMD Shell Command Line Syntax
• (%~#, %~f#, %~n# etc. special page) Command Line arguments (Parameters)