It's been a couple decades since I had a need for PL/I. Mostly I used Assembler for working with the operating system and channel programming.

PL/M last I looked was not allowed outside IBM development labs, but I see a bunch of stuff coded in PL/M. My impression is that it's basically a bunch of macros wrapped around Assembler instructions in a common quest to eliminate branch instructions.

But remember that every IF and loop is implemented with branches under the covers.