I'm trying to use a While Loop to prompt for a response.  I want to force the person to type in one response or another.  I can get this to work this way:

while ($favcolor -ne "blue") {$favcolor = Read-Host "What is your favorite color?"}

If the user types anything other than "blue", they get prompted again.

But when I try and use multiple options, it doesn't work.

while ($favcolor -ne ("blue" - or "green" -or "black")) {$favcolor = Read-Host "What is your favorite color?"}

I've tried several different ways of writing this but I can't seem to figure it out.  Am I going about this the right way?  Is there a better way to do it?  I want to be able to have a list of acceptable answers and then use that variable later in the script.

try something like this:

while ( ("blue","yellow","red") -notcontains $favcolor)
{$favcolor = read-host " favourite color?"}

Brandon did a good job explaining this on his blog http://bsonposh.com/archives/343

As for your example, I would suggest something a little more...

If you really want a one liner...  -match/notmatch can take a regular exression.  Not only is this faster but it's easier to read!

while ($favcolor -notmatch "(blue|green|black)") {$favcolor = Read-Host "What is your favorite color?"}

If your not tied to a one liner, then I prefer nesting a switch withing the loop. best of both worlds imo.

$favcolor = ""
while ($favcolor -eq "")
{
    switch (Read-Host "What is your favorite color?")
        {
        "blue"  {$favcolor = "blue"}
        "black" {$favcolor = "blue"}
        "green" {$favcolor = "blue"}
        default {Write-Host "Invalid selection, please try again"}
    }
}

hope that helped
~glenn

np... glad to help