Powershell function to check validity of a CAS number
What is a CAS? - See http://www.cas.org/content/chemical-substances/faqs - TL/DR- it's a number that identifies a chemical. If you don't know what one is already, you're probably not going to want to use this function.
PS C:> #Example of test-CAS.
PS C:> #This first one uses the CAS Number of Caffeine. This should return "true" as it is valid
PS C:> test-CAS 58-08-2
True
PS C:> #This second example uses an invalid CAS and should return "false"
PS C:> test-CAS 58-08-99
False