compare-object left or right side only
there is no option like that for that cmdlet, however you could create a filter (in your profile for example) and then use it to filter the result :something like
filter leftside{param( [Parameter(Position=0, Mandatory=$true,ValueFromPipeline = $true)] [ValidateNotNullOrEmpty()] [PSCustomObject] $obj ) $obj|?{$_.sideindicator -eq '<='}}usage
compare-object $a $b | leftside
You can also add -property SideIndicator and use an if statement for it.
$Missing = compare-object $Old $new -Property Name,SideIndicator ForEach($Grp in $Missing) { if($grp.sideindicator -eq "<=") { # Do Something here } }