Here are some other interpreters if you’re curious how this design compares.

Microsoft 8080 BASIC interpreter [0] is a commented disassembly. An improved version is at [1]. The book Programmers at Work also has notes on the design.

[2] is a z80 BBC BASIC interpreter.

[0] http://altairbasic.org/

[1] https://github.com/option8/Altair-BASIC

[2] https://github.com/jblang/bbcbasic-z80

Any suggestions for CBM BASIC?

Commodore licensed BASIC from Microsoft in 1977.

You have the original ASM disassembled, ROM, kernal and comments at https://www.pagetable.com/c64ref/c64disasm/

Or, although not what you asked: https://github.com/microsoft/GW-BASIC