How to match against an input to rule (non-literal) string?

[davidOSUL]

e.g:
For matching against literal strings we can do:

pub rule matchIt() = "matchesThisLiteralString"

but is there anyway to do something like:

pub rule matchIt(x: &str)  = <matches if equals x> 

[kevinmehall]

##parse_string_literal(x) -- Example from the test suite

The ## syntax is a semi-undocumented feature that calls a method on the input string, and it passes the same arguments as the ParseLiteral::parse_string_literal method expects.