CLI Output
    -- Launched AGI Script /var/lib/asterisk/agi-bin/agent-getname.pl
  agent-getname.pl|1245: Setting callerid name to: Firstname Lastname
    -- AGI Script agent-getname.pl completed, returning 0
    -- Executing Set("SIP/8117-d30e", "CALLERID(number)=1245") in new stack
    -- Executing Set("SIP/8117-d30e", "CALLERID(name)=Firstname") in new stack

Extensions
        exten => s,3,agi(agent-getname.pl|${AGENTBYCALLERID_${CALLERIDNUM}})
        exten => s,4,Set(CALLERID(number)=${AGENTBYCALLERID_${CALLERIDNUM}}) ; Use the agent ID
        exten => s,5,Set(CALLERID(name)=${AGENTNAME}) ; Set the Agent name


AGI
                        $agi->verbose("Setting callerid name to: $2");
                        $agi->set_variable("AGENTNAME", "$2");