drothlis/pretty-symbols — pull request #7 by tobias (2013-10-14 00:49:09+00:00)
Title: Support specifying the match index to replace.

This allows for replacing only a portion of the regex, which is lets
you replace a character only when it is followed by another specific
character. For example, `#()` defines a lambda in Clojure. but I don't
want to replace every `#`. With this patch, the following works:

(add-to-list 'pretty-symbol-patterns
'(?λ lambda "\\(#\\)(" (clojure-mode) 1))