asterisk users - Oct 2006 - dialplan issue - 1& 0 should be false

Helo List,

I'm having an issue using the AND (&) operator in the code of my
dialplan.
The dial plan is coded to detect inbound DTMF digits from callers. key
"1"
is equivalent to "yes" and key "2" is equivalent to
"no" in my dial plan.
When a caller presses 1, yes is passed as a varialble and same when 2 is 
pressed a "no" is passed.

When the values are both set to "yes" the evaluation of the AND
operation of
the following expression is true and works fine going to the correct 
priority,

exten => s,3,Gotoif($[${test11} = yes]& $[${test12} = yes]?7:4)

Debug output

-- Goto (test-check,s,1)
    -- Executing NoOp("SIP/123-e131", "yes") in new stack
    -- Executing NoOp("SIP/123-e131", "yes") in new stack
    -- Executing GotoIf("SIP/123-e131", "1& 1?7:4") in
new stack
    -- Goto (test-check,s,7)

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