NAME
    POE::Session::Cascading - Stack-like POE Sessions

AUTHOR
    Matt Cashner (eek+cpan@eekeek.org)

DATE
    $Date: 2005-12-07 01:46:13 -0500 (Wed, 07 Dec 2005) $

SYNOPSIS
        POE::Session::Cascading->new(
            name => 'foo',
            events => [
                'state1' => \&state1,
                'state2 => \&state2,
            ],
        );

        sub state1 {
            my %args = @_;
            $args{KERNEL}->post('somewhere','somestate');
            # [ snip ]
        
        }
    
        sub state2 {
            my %args = @_;
            # [ snip ]
        
            $args{SESSION}->stop;
        }

DESCRIPTION
  INTRODUCTION
    POE::Session::Cascading provides a stack-like session for POE. Another
    way of saying it is that a Cascading session is like a big switch
    statement. In the above example, when "state1" is called in session
    "foo", &state1 gets executed. When it finishes, "state2" gets fired and
    &state2 gets executed. If "state2" is called in session "foo", only
    "state2" will get executed.

  CONTROLLING PROPOGATION
    Each state can decide whether chain propogation should continue or not.
    If the state wishes to stop chain propogation, it must call
    "$args{SESSION}->stop". Otherwise, chain propogation will continue. A
    state can call "$args{SESSION}->go" to forcibly allow chain propogation.
    This is largely superflous as this is the default option.

    It would be appropriate to return call "stop", for instance, if the
    state has determined that further action by this chain is unnecessary or
    undesirable. The state might launch a different chain and cal "stop" to
    shutdown the current chain's propogation.

  LAUNCHING A CHAIN
    To initiate a chain, post a call to the relevant state with the
    session's name. For instance, to activate the chain in the example
    above, one would write:

        $poe_kernel->post('foo','state1');

    Arguments passes to POE's post method will be passed directly to the
    state and those which follow it.

  WRITING A STATE
    Cascading states are a bit different from the usual POE states, mainly
    in the argument list. Cascading states are passed a hash, containing
    three entries. "SESSION" contains a reference to the current session's
    object. "KERNEL" contains a reference to the POE kernel. "ARGS" contains
    an array reference of the arguments passed to the state.

    Cascading states can do anything perl can. Cascading states are passed a
    hash, containing three entries. "SESSION" contains a reference to the
    current session's object. "KERNEL" contains a reference to the POE
    kernel. "ARGS" contains an array reference of the arguments passed to
    the state, including any data passed from the previous state..

METHODS
  new()
        POE::Session::Cascading->new(
            name => 'foo',
            events => [
                step1 => \&step1,
                step2 => \&step2,
                step3 => \&step3,
            ]
        );

  stop
        $args{SESSION}->stop;

    Instruct the current session to stop chain propogation.

  go
        $args{SESSION}->go;

    Instruct the current session to continue chain propgation.

  swap
        $args{SESSION}->swap($state1, $state2);
    
    Reorder the event stack. Swap two states in the stack.

BUGS AND KNOWN ISSUES
    * Cannot register or unregister a stack element at runtime
    * Stack requires outside influence to start (is this actually a
    problem?)

LICENSE
    Copyright (c) 2002, Matt Cashner. All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are
    met:

    * Redistributions of source code must retain the above copyright notice,
    this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
    notice, this list of conditions and the following disclaimer in the
    documentation and/or other materials provided with the distribution.
    * Neither the name of Matt Cashner nor the names of its contributors may
    be used to endorse or promote products derived from this software
    without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
    IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
    TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
    PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
    OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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