It's the delimiter parameter, but it looks like you can only pass it one character, not an array.
You could always just hard code it into line 294. Change this:
if (event.which==event.data.delimiter.charCodeAt(0) || event.which==13 )
To this:
if (event.which==event.data.delimiter.charCodeAt(0) || event.which==59 || event.which==13 )
Working demo: http://jsfiddle.net/kbwqr/