We can validate the provided value of a new property called version with a validate block and, for example, a regex expression, as shown in the following code:

Puppet::Type.newtype(:mynewtype) do
   ...
   newproperty(:version) do
     validate do |value|
       fail("Invalid version specified") unless value =~
         /^(d+.)?(d+.)?(*|d+)$/
     end
   end
   ...
 end