Looks like Elixir pattern matching, where to match something like a JSON object, you basically write something that looks just like the object, with identifiers (probably the wrong name) where you want the matched data filling in.
Interestingly backwards from normal querying — instead of a large number of records and one query, you’ve got a large number of queries and one record. Presumably this is good when you’re watching data being streamed instead of data at rest.
The reference to the “|” operator in grep reminded me that this is probably implemented as a Nondeterministic Finite State Automaton, which is used in regex matchers and the “lex” tool. I’ve always liked the idea of these — you take a normal state machine and run it in a Many-Worlds universe, following all possibilities and never collapsing the wavefunction. Then you map the resulting states to a normal state machine you actually run.
Matching on exact values seems a bit limiting, though. It’s probably straightforward to extend the state matching to handle simple comparisons like “temp > 0”, but it complicates the pattern specification.