the differences between PM and MPASM?
PM is the in-built assembler in PBP. MPASM comes from MPLAB toolchain. If you're the kind that likes to read .LST files and learn how to ASM, PM is the better option simply because it generates shorter LST files. For Darrells code to work, you WILL need to use MPASM as he uses a lot of features present only in MPASM (esp. MACROS)

INCLUDE "ReEnterPBP.bas" ; Include if using PBP interrupts
If you want to write BASIC code within your interrupt section, you should use this. What it does is to save the state of the PBP variables on entering the ISR(interrupt service routine) and restore it back on exit. That way, you do not have to write ASM code in the ISR.