gistfile1.ps1

$script = {
    ($InputObject, $2to1Ready, $1to2Ready, $2to1End, $1to2End) = $($input)
    $InputObject_ = $InputObject.GetNewClosure()
    try {
        do {
            & $InputObject_ | 
                ForEach-Object {
                    $_
                    [Void]$2to1Ready.Set()
                    [Void]$1to2Ready.WaitOne()
                    if ($1to2End.WaitOne(0)) {
                        break
                    }
                }
        } until ($true)
    } finally {
        [Void]$2to1End.Set()
        do {
            [Void]$2to1Ready.Set()
        } until ($1to2End.WaitOne(1))
    }
}

$runspace = [Management.Automation.Runspaces.RunspaceFactory]::CreateRunspace()
try {
    $runspace.Open()
    $pipeline = $runspace.CreatePipeline($script)
    [Void]$pipeline.Input.Write({ 11..20 })
    $2to1Ready = New-Object Threading.AutoResetEvent $false
    [Void]$pipeline.Input.Write($2to1Ready)
    $1to2Ready = New-Object Threading.AutoResetEvent $false
    [Void]$pipeline.Input.Write($1to2Ready)
    $2to1End = New-Object Threading.ManualResetEvent $false
    [Void]$pipeline.Input.Write($2to1End)
    $1to2End = New-Object Threading.ManualResetEvent $false
    [Void]$pipeline.Input.Write($1to2End)
    $pipeline.Input.Close()
    $pipeline.InvokeAsync()

    try {
        do {
            & { 1..10 } | 
                ForEach-Object {
                    [Void]$2to1Ready.WaitOne()
                    if ($2to1End.WaitOne(0)) {
                        break
                    }
                    if (!$pipeline.Output.EndOfPipeline) {
                        ($_, ($pipeline.Output.NonBlockingRead() | % { $_ })) -join ', '
                    }
                    [Void]$1to2Ready.Set()
                }
        } until ($true)
    } finally {
        [Void]$1to2End.Set()
        do {
            [Void]$1to2Ready.Set()
        } until ($2to1End.WaitOne(1) -and $pipeline.PipelineStateInfo.State -ne [Management.Automation.Runspaces.PipelineState]::Running)
        
        if ($pipeline.PipelineStateInfo.State -eq [Management.Automation.Runspaces.PipelineState]::Failed) {
            Write-Error -Exception $pipeline.PipelineStateInfo.Reason
        }
        
        $pipeline.Dispose()
    }
    
} finally {
    if ($null -ne $runspace) {
        $runspace.Dispose()
    }
}