'let :=' for immediate evaluation in assignment.  Does this work
for included files?

Default parameters, ie:
  goal foo (name, release = true) = ...
You might only allow defaults to be added to the end, or you
might allow goals to be called with labelled parameters.

Functions, eg. wildcard("*.c").  These should be defined as shell
scripts with a selection of common functions defined in stdlib.

Fix: You must use 'all ()' on the command line.