Provide ability to write pattern matchers for sequential things that also check type

[sritchie]

For example, splicing in (up '?a '?b) should create a pattern matcher that checks for up status and interprets the entries, when the structure is turned into a seq, as matcher grammar.

This would be helpful with quaternions, hypercomplex numbers, structures, series (for some prefix matches!) and matrices.

There are clues for this in the "Software Design for Flexibility" book's implementation, for sure.