_start 
_start is a session's initialization event. It tells a session that the Kernel has allocated and initialized resources for it, and it may now start doing things. A session's constructors invokes the _start handler before it returns, so it's possible for some sessions' _start states to run before $poe_kernel->run() is called.

Every session must have a _start handler. Its parameters are slightly different from normal ones.

SENDER contains a reference to the new session's parent. Sessions created before $poe_kernel->run() is called will have KERNEL as their parents.

ARG0..$#_ contain the parameters passed into the Session's constructor. See Session's new() and create() methods for more information on passing parameters to new sessions.