besideCN seems to have stopped working

[Gerry Prosser]

besideCN is used to display capo settings along with guitar chord names, but with 2.15.39 I get error message 'Unbound variable: $which-side'

the last working score I have was compiled with 2.15.13

besideCN = #(define-music-function (parser location which-side added-text) (integer? string?) #{\once \override ChordNames.ChordName #'stencil = #(lambda (grob) (ly:grob-set-property! grob 'text (markup #:put-adjacent 0 $which-side ; #LEFT or #RIGHT
(ly:grob-property grob 'text) $added-text)) (ly:text-interface::print grob)) #})

Chords = \new ChordNames \chordmode {
  \besideCN #LEFT "Capo1 " d1 fis2:m7 b2:m e1:m7 a
}

any clues, anyone, please ?

Gerry