[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "Y"):

function Test-ShouldProcess
{
    [CmdletBinding(SupportsShouldProcess = $true)]
    PARAM (
        [Parameter(ValueFromPipeline = $true)]
        $InputObject
    )

    PROCESS
    {
        if ($PSCmdlet.ShouldProcess($InputObject, "Do stuff to it"))
        {
            Write-Host "Doing stuff to $InputObject"
            Test-ShouldProcess_InnerFunc -InputObject $InputObject
        }
    }
}

function Test-ShouldProcess_InnerFunc
{
    [CmdletBinding(SupportsShouldProcess = $true)]
    PARAM (
        [Parameter(ValueFromPipeline = $true)]
        $InputObject
    )

    PROCESS
    {
        if ($PSCmdlet.ShouldProcess($InputObject, "Do internal stuff to it"))
        {
            Write-Host "Doing internal stuff to $InputObject"
        }
    }
}

"item1", "item2" | Test-ShouldProcess -Confirm

Confirm
Are you sure you want to perform this action?
Performing the operation "Do stuff to it" on target "item1".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "Y"): A
Doing stuff to item1

Confirm
Are you sure you want to perform this action?
Performing the operation "Do internal stuff to it" on target "item1".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "Y"): A
Doing internal stuff to item1
Doing stuff to item2

Confirm
Are you sure you want to perform this action?
Performing the operation "Do internal stuff to it" on target "item2".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [S] Suspend  [?] Help (default is "Y"): A
Doing internal stuff to item2