After numerous hours spent trying unsuccessfully to fix this problem by following the instructions outlined on a few StackOverflow posts, Jordan presented a recipe for fixing this problem (that actually fixed the problem) today.
The essence of the issue is that the readline package that gets installed with REE is by default some bastard version that lags, at least on our Ubuntu and Mint installations. Installing the rvm readline package did not fix it for either of us, nor did an assortment of experiments on compiling REE with different options. Here’s what did:
$> sudo apt-get remove libreadline6-dev
$> sudo apt-get install libreadline-gplv2-dev
$> rvm remove ree
$> rvm install ree
One problem you may encounter is that if you’re avoiding newer versions of Ubuntu until admit defeat about Unity, the “libreadline-gplv2-dev” package is by default only present in Oneiric and above. Here’s where I found the package versions that worked with Maverick: https://launchpad.net/~dns/+archive/test0/+sourcepub/2252776/+listing-archive-extra. After downloading the packages from this link, the install sequence became
$> sudo apt-get remove libreadline6-dev libreadline5
$> sudo dpkg -i libreadline5_5.2-9~maverick0_amd64.deb
$> sudo dpkg -i libreadline-gplv2-dev_5.2-9~maverick0_amd64.deb
$> rvm remove ree
$> rvm install ree