Meta languages normally imply that you can program the language syntax itself via an extensive macro system.

But then, I'm not sure perl has that facility at all.

The term "meta-language" shouldn't be used to identify a specific language; it's a general term for a language that describes or manipulates another language(s). For instance, the rules language for XTRAN, our Expert System, is a meta-language, and we call it "meta-code", because it manipulates many different computer languages (including itself!), as well as data and text.

A well-known ML example is Backus-Naur Form (BNF), which is a meta-language for specifying well-formed statements in a language. We use BNF to drive XTRAN's parsing engine, which executes the BNF at parse time.