I remember being bitten my `which` on Solaris not giving return codes. I was not yet aware of `hash` or `command` At $PREVIOUS_JOB, I tried to maintain dotfile

I remember being bitten my `which` on Solaris not giving return codes. I was not yet aware of `hash` or `command` At $PREVIOUS_JOB, I tried to maintain dotfiles that could be used on Solaris and RHEL interchangably, and I had a bunch of conditionals for enabling various completions.