Wow, big trip down memory lane here because my first job was on a Prime mini-computer! Wrote a complete system using CPL scripts (with the occasional bit of Fortran thrown in) on Primos.
Shame to hear that Prime / Primos is now defunct but that job was back in the 80's!
Primos wasn't much good compared to the commercial Unixes that were appearing. It did have one nice-ish feature late in it's history; the CPL scripting language.