Used Cadence Skill
I worked with Cadence Skill about 14 years ago. I found it quite useful, but this variant of lisp also allowed a c-like syntax and my coworkers had no intention of learning to use the lisp syntax, limiting the degree to which I could use it myself.
I first encountered lisp in college, 40 years ago. It didn't make a lot of sense to me at the time, but when I was teaching myself Skill I pulled out my college textbook (which I still had for some reason) and NOW it made sense. I guess it just takes a while for it to sink in. Of course it helps to have a reason to learn it.