Writing a function

[Rok Kršmanc]

Hi!

I would like to write a function for the next music expression:
\once \override TextScript.extra-offset = #'(0 . 1)
c^"o"

Here is my try:
f =
#(define-music-function (parser location offset music)
  (number? ly:music?)
  #{
    \once \override TextScript.extra-offset = #'(0 . $offset)
    $music ^"o"
  #})

When I call this function:
\f #1 c

I get syntax error:
unexpected '^'

What am I doing wrong?