When you want the behavior of a while loop and would like 1 iteration to happen before any condition is checked, the do…while and do…until loops are a good choice.

$answer = 4
do {
  $input = Read-Host "Guess my number"
} while ($input -ne $answer)
Write-Host "Correct!"

The above example starts the loop with the keyword do and the loop body will execute once. After one iteration, the condition $input -ne $answer defined after the keyword while will be checked. If the condition is true, the loop will continue.

The do…while allows Read-Host to execute and set the value of $input, which is then checked after the first loop. The output of the above example could look like this:

Guess my number: 5
Guess my number: 3
Guess my number: 4
Correct!

do…until is the same as do…while except when the condition is true, the loop will exit. The above example with a do…until will use the -eq operator in the condition.

$answer = 4
do {
  $input = Read-Host "Guess my number"
} until ($input -eq $answer)
Write-Host "Correct!"

Remember that these loops are helpful when you want at least one loop iteration to happen, regardless of your code state.