Can be given only once. Can be user more than once. That means that at perl, python or gcc must be installed in order to build and run that package. There are no 'negative' dependecies saying 'package foobar must not be installed'. The Value may contain balnks.
Suggestions are wellcome.
Suggestions for that value list are welcome. Cathegory I had a good reason for not including that information in the ext files. With time the number of extensions will grow and we will have to make a major redesign of the ext directory structure. The number of architectures and sub-architectures will grow very fast. So a simple test in the .ext file is much better than a flag since can check for endian, cpu type, word-lenght, whatever.