You should definitely use version 5. Version 4 is old, limited, and no
longer maintained. Its last patch (4.036) was in 1992. The last production
release was 5.003, and the current experimental release for those at the
bleeding edge (as of 27/03/97) is 5.003_92, considered a beta for
production release 5.004, which will probably be out by the time you read
this. Further references to the Perl language in this document refer to the
current production release unless otherwise specified.