Replacing \set stanza with custom verseNumber

[Tom Dickson]

It doesn't work correctly - it appears Scheme doesn't like the second  
use of the variable?

verseNumber = #(define-music-function (parser location markp) (string?)
#{
    \set vocalName = $markp
    \set shortVocalName = $markp
    \override InstrumentName #'X-offset = #2
    \override InstrumentName #'font-series = #'bold
#})

is what I'm trying - but it's not the same as putting the code in  
place. The only difference I can see is the code looks like this:

    \set vocalName = #"3."
    \set shortVocalName = "3."
    \override InstrumentName #'X-offset = #2
    \override InstrumentName #'font-series = #'bold

and doesn't have the # sign in front of the second "3."

Scheme is confusing me.

-tom