Dial Plan from extensions.conf:
[Q_answer]
exten => s,1,NoOp(I exist!)
same => n,Return

[Q_inbound]
exten => s,1,Answer()
same => n,Gosub(Q_answer,s,1)
same => n,Queue(paul,,,,,,,Q_answer))

[pspp-program]
exten => _+X.,1,Goto(pspp-program,${EXTEN:1},1)
exten =>_X.,1,Goto(Q_inbound,s,1)


Simple test Call results in the following CLI Verbose Output:


    -- Executing [12130000000@pspp-program:1] Goto("PJSIP/o1_inbound1-00000000", "Q_inbound,s,1") in new stack
    -- Goto (Q_inbound,s,1)
    -- Executing [s@Q_inbound:1] Answer("PJSIP/o1_inbound1-00000000", "") in new stack
       > 0x7ff6f42ae8e0 -- Probation passed - setting RTP source address to 0.0.0.1:14664
    -- Executing [s@Q_inbound:2] Gosub("PJSIP/o1_inbound1-00000000", "Q_answer,s,1") in new stack
    -- Executing [s@Q_answer:1] NoOp("PJSIP/o1_inbound1-00000000", "I exist!") in new stack
    -- Executing [s@Q_answer:2] Return("PJSIP/o1_inbound1-00000000", "") in new stack
    -- Executing [s@Q_inbound:3] Queue("PJSIP/o1_inbound1-00000000", "paul,,,,,,,Q_answer)") in new stack
    -- Started music on hold, class 'default', on channel 'PJSIP/o1_inbound1-00000000'
    -- Called PJSIP/paulstation1
    -- Called PJSIP/payphonetest6
    -- Called PJSIP/payphonetest4
    -- Called PJSIP/payphonetest3
    -- PJSIP/payphonetest3-00000004 connected line has changed. Saving it until answer for PJSIP/o1_inbound1-00000000
    -- PJSIP/payphonetest4-00000003 connected line has changed. Saving it until answer for PJSIP/o1_inbound1-00000000
    -- PJSIP/payphonetest6-00000002 connected line has changed. Saving it until answer for PJSIP/o1_inbound1-00000000
    -- PJSIP/paulstation1-00000001 connected line has changed. Saving it until answer for PJSIP/o1_inbound1-00000000
    -- PJSIP/payphonetest3-00000004 is ringing
    -- PJSIP/payphonetest4-00000003 is ringing
    -- PJSIP/paulstation1-00000001 is ringing
    -- PJSIP/payphonetest6-00000002 is ringing
    -- PJSIP/paulstation1-00000001 answered PJSIP/o1_inbound1-00000000
    -- Stopped music on hold on PJSIP/o1_inbound1-00000000
    -- PJSIP/paulstation1-00000001 Internal Gosub(Q_answer),s,1) start
[Sep 25 13:10:14] ERROR[14470][C-00000001]: app_stack.c:594 gosub_exec: Attempt to reach a non-existent destination for Gosub: (Context:Q_answer), Extension:s, Priority:1)
    -- Channel PJSIP/paulstation1-00000001 joined 'simple_bridge' basic-bridge <7fb2e354-af13-4f34-8c29-49fbde51d509>
    -- Channel PJSIP/o1_inbound1-00000000 joined 'simple_bridge' basic-bridge <7fb2e354-af13-4f34-8c29-49fbde51d509>
       > Bridge 7fb2e354-af13-4f34-8c29-49fbde51d509: switching from simple_bridge technology to native_rtp
       > Locally RTP bridged 'PJSIP/o1_inbound1-00000000' and 'PJSIP/paulstation1-00000001' in stack
       > 0x7ff6f42b8b80 -- Probation passed - setting RTP source address to 47.148.20.115:3000
       > 0x7ff6f42b8b80 -- Probation passed - setting RTP source address to 47.148.20.115:3000
    -- Channel PJSIP/o1_inbound1-00000000 left 'native_rtp' basic-bridge <7fb2e354-af13-4f34-8c29-49fbde51d509>
  == Spawn extension (Q_inbound, s, 3) exited non-zero on 'PJSIP/o1_inbound1-00000000'
    -- Channel PJSIP/paulstation1-00000001 left 'native_rtp' basic-bridge <7fb2e354-af13-4f34-8c29-49fbde51d509>