The Preferred Executable Format (PEF) was introduced with the first
Power Macs as the container format for PowerPC code. Almost all PowerPC
code in the classic Mac OS is in PEF containers. (PEF containers were
also used by BeOS for PowerPC, and occasionally by Mac OS X. Apple also
adapted them to include 68k code for the "CMF-68k" runtime environment,
but this feature was rarely used.)

Patchpef lets you make small changes to the code section of a PEF
container.

Vasm with the "mot" syntax module ("vasmppc_mot") is required to
assemble code.

Syntax: patchpef.py <input> <output> <offset1> <code1> ...

Examples:
patchpef.py DataForkPEF USB.rsrc//nlib/-20777/USBFamilyExpertLib 0x1030 :'initing USB expert' 0x11B0 :'done initing USB' 0x10C8 :'about to call function (will log return)' 0x10CC :r3