SCRIBE:  Matt Fulgo

Command			comment
eval {non-builtin}	have code
eval {builtin}		"case" statement: use strncmp
			use a function for each command
echo [w1] [w2] [...]	have code (see debug)
quit w			exit or return
			what about background processes?  cleanup?
quit			have to record the exit status of the last command
			what if $? is UNDEF?


while(there is a command)
  word[] = (parse)
  xword[] = (substitute)
  if (-x) display xword[] // debug flag
  ... code ...
  if(builtin) eval builtin
  else eval nonbuiltin