[colanderman]

Please don't let Ruby's leaky dynamic action-at-a-distance shoddy excuse for metaprogramming and DSLs scare you away from real metaprogramming and DSLs.

Real metaprogramming doesn't involve action-at-a-distance and flaky dynamic interpretation. Real DSLs don't let you "peek behind the curtain" and therefore don't leak. True metaprogramming systems and DSLs don't let you flout "convention" and get into trouble as RoR does.

Introspection and a dynamic unstratified language do not make a metaprogramming system. High-level well-founded language manipulation constructs do.

Conventions and overloaded operators do not make a DSL. A well-defined grammar and interpreter do.

See OCaml's module system for an example of metaprogramming done right. It is simple to use and gives strong static guarantees. If it compiles, it will run without crashing; else the compiler will give clear error messages if it's unhappy.

See YACC, SQL, and XPath for examples of DSLs done right (albeit arguably abtrusely). They do not leak by design, since they do not let you "peek behind the curtain" which is the #1 way to get yourself (or others) in trouble with DSLs.