<Jafet> (echo \'#!/bin/sh\'; echo \'a() { p=$(echo -n $(ps -p $0 -oppid | tail -1)); if egrep " \\| cat\\$" /proc/$p/cmdline; then ps -p $0 -ocmd | tail -1; else a $p; fi }\'; echo \'a $$\') > bin/quine2

D-modules are just modules over the ring of differential operators. Taneb invented them.