I just created my first DSL, called Nemesis, in Haskell. It's modeled after Rake.

A single file named Nemesis containing dependency specifications, something like this:

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nemesis = do

  task "dist" $ do
    sh "cabal clean"
    sh "cabal configure"
    sh "cabal sdist"

  task "i" (sh "ghci -isrc src/System/Nemesis.hs")

  task "manifest" $ do
    sh "find . | grep 'hs$' > manifest"

I'm planning to use Nemesis instead of Rake from now on, since Nemesis compiles to machine code and can be blazingly fast. I'm happy :)