Answer by Gill for Use -notlike to filter out multiple strings in PowerShell

Scenario: List all computers beginning with XX1 but not names where 4th character is L or P

Get-ADComputer -Filter {(name -like "XX1*")} | Select Name | Where {($_.name -notlike "XX1L*" -and $_.name -notlike "XX1P*")}

You can also count them by enclosing the above script in parens and adding a .count method like so:

(Get-ADComputer -Filter {(name -like "XX1*")} | Select Name | Where {($_.name -notlike "XX1L*" -and $_.name -notlike "XX1P*")}).count