ColdBox/CF dummy question

Hello,

Why something like this works
     rc.varname = tagstripper('Event.getValue(rc.varname)')
and this one receives error ('rc.varname is undefined')
     rc.varname = tagstripper('rc.varname')

I mean is it maybe somehow connected with fact tha in cf structs are returne by reference ?

Thanks with advance.
Regards,
Bartek.