problem with mapconcat

[Christian Wittern <cwittern@gmail.com>]

Hi there,

I am trying to build a regex with lisp, which inserts a certain string 
into another string between each character, for example "abc" should 
turn into "a/b/c". 

With mapconcat, I think this should work:

(mapconcat 'identity (string-to-list "abc") "/")

since the description for mapconcat says

(mapconcat FUNCTION SEQUENCE SEPARATOR)

However, when I try to evaluate this in Emacs 23.1, here it throws the 
following error:

Debugger entered--Lisp error: (wrong-type-argument sequencep 97)
  mapconcat(identity (97 98 99) "/")
  eval((mapconcat (quote identity) (string-to-list "abc") "/"))

I wonder what I am doing wrong or if there is another way to achieve
 what I am trying to do.

Any help appreciated,

Christian