#!/usr/bin/perl
use strict; use warnings;
use Data::Dumper;

use Coro::State;
  
sub yield {
    my $retval = $Monad::retval = shift;
    $Monad::cDo->transfer($Monad::cMain);
    return $retval;
}

sub Do (&) {
    my $Do = shift;
    local $Monad::retval;
    local $Monad::cMain = Coro::State->new;
    local $Monad::cDo   = Coro::State->new(sub {
        $Do->();
        yield undef;
    });

    $Monad::cMain->transfer($Monad::cDo);
    my $first = $Monad::retval;
    {
        $Monad::cMain->transfer($Monad::cDo);
        last unless my $retval = $Monad::retval;
        print "Gots $retval ($first)";
        redo;
    }
    };

Do {
    my $x = yield 3;
    my $y = yield 4;
    my $z = yield 5;
    print "All $x,$y,$z\n";
};