In your example, you have curly (smart) quotes. Please tell me you didn't copy paste that from your script! If the server names have hyphens, they should be in quotes. Just because the script works on one computer it doesn't mean it will work on all computers. If you have trailing spaces in your list, it will bite.
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Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.