Regex op specs can currently be used with non-ordered maps or sets but may give confusing errors.
Cause: Spec fails because the first value of the map (the tuple pair `["foo" "bar"]`) is not a keyword
Proposed: Regex op specs currently check `coll?`, which will pass unordered collections like sets or maps which are unlikely to be useful for positional regex specs. If really needed. Instead narrow that check to `sequential?`. On failure, use explain pred that describes the actual check (current one just repeats the regex spec instead).
After message actually tells you what's wrong:
Screened by: Chouser - while making unordered colls invalid is the intent of the patch, a gray area is that of sorted colls (sorted sets, etc). These could have been matched with the prior impl, but will not be after the change. See comments for more examples.