I would recommend taking a quick look at how SCons and Conary use python. You may also want to consider implementing your DSL using a python parser generator such as Ply.

SCons - http://www.scons.org/doc/HTML/scons-man.html#lbBB

Conary - http://wiki.rpath.com/wiki/Conary:Recipe_Structure

Ply - http://www.dalkescientific.com/writings/NBN/parsing_with_ply...