Use official 7-Zip in an isolated VM or sandbox.
For legitimate reverse engineering of very old P-code (pre-2010), you may find limited success with community scripts on GitHub, but always verify in a safe environment. For everyone else, focus on ethical alternatives. matlab pcode decoder7z best
Open .p in a hex editor or Notepad++ – sometimes original comments remain visible. Use official 7-Zip in an isolated VM or sandbox