string-match unbound

[Piers Titus]

> I'm not top posting.

% The function string-match is not available, while it is in GUILE.
% Lilypond gives error: Unbound variable: string-match
% This bug has been noticed before, see
http://lilypond-s-support-for-tablatures.3383434.n2.nabble.com/slides-td3533701i20.html
% (this is just a test file, which doesn't have a meaning if there was no error,
the real problem is redefining the /clef command with code copied from
scm/parser-clef.scm)
\version "2.12.3"

clef = #(define-music-function (parser location clef-name) (string?)
   (string-match "^(.*)([_^])([1-9][0-9]*)$" clef-name))
\relative c'' {
  \clef "treble_8"
  c
}