How can I call an older version of a gem from the commandline?

Question

Say I have two versions of a gem installed (somegem versions 0.10.6 and 0.10.5) and I want to run the earlier version from the commandline. Do I have to uninstall the newer

Answer 1

somegem _0.10.5_ /path/to/dir

No link to documentation, because apparently there isn't any.