I’m not sure this is the best, but:
function A{
Param([scriptblock]$FunctionToCall)
Write-Host "I'm calling $($FunctionToCall.Invoke(4))"
}
function B($x){
Write-Output "Function B with $x"
}
Function C{
Param($x)
Write-Output "Function C with $x"
}
PS C:\WINDOWS\system32> A -FunctionToCall $function:B
I'm calling Function B with 4
PS C:\WINDOWS\system32> A -FunctionToCall $function:C
I'm calling Function C with 4
PS C:\WINDOWS\system32> A -FunctionToCall { Param($x) "Got $x" }
I'm calling Got x