Barge-in with two way audio

I am trying to make a small call center where users can retrive all kinds of information from IVR (i have done that with Perl AGI) and be connected with operater as soon as it is available. So what I have here is working IVR (with lot’s of searching through databases and playingback that info - that’s why AGI is needed) but operator should be allowed/enabled to barge into that call (Zap channels) without user having to do anything and continue to talk with the user. If user or operater should later desire to return user to IVR one of them should press some key(s).

I can’t find the solution for stoping the AGI execution (when operater is available) and bridge the user call with operator. Any ideas how this can be done?