Look for use cases for $input

[IMJLA]

$input is ancient PowerShell v1

In a scriptblock it contains every input to the scriptblock at that point in time

in the end block, $input contains every input

It is faster than accumulating input in the process block

Watch Out: $input can only be read once

[IMJLA]

suspected use case in PsRunspace module

[IMJLA]

Implemented in Split-Thread only due to simplest direct replacement

Need to evaluate impact to see if it is worth rearchitecting any other functions to take advantage of the perf improvement