Every time I have issues with rvm (which seems often) or rbenv (occasionally, I use it less), I'm reminded that Modules (http://modules.sourceforge.net/) takes care of this path fiddling and more. Yeah, it's old and it's in TCL and it doesn't solve the "how do I build a new ruby and gemset" problem but it's been working for years on the "how do I switch path" problem. I use module when I build .deb of Ruby and gems.