I remember hearing that originally the Unix shell had control structures (e.g. if, while, case) implemented through external commands.  However, I can't see this reflected in the source code.  The 7th Edition Bourne shell has these commands built-in (usr/src/cmd/sh/cmd.c), while the 6th Edition (usr/source/s2/sh.c) seems to lack them completely.

The only external command I found was glob, which performed wildcard expansion.

Am I missing something?  Was this implemented in a version that was never released?  If so, does anyone know how this implementation worked?  (Nested commands might require holding some sort of globally accessible stack.)