In the real world you seldomly have an exactly nailed-down specification of anything. If you're lucky enough to do something as basic as parsing URIs or JSON, you have, but normally not.
Writing a recursive descending parser isn't hard, as you said, but it's again something that needs testing, you need put some effort into it to get good error messages from it - and why would you repeat such a task? Also you often need to write a lexer -- another burden of which Perl 6 grammars free you.
Regarding your thoughts about abstract languages: Perl 6 provides tools to make experimenting with them rather easy, which helps learning about them.
I've made the experience that a reasonably good programmer can write some 20 lines of Perl code, and it does what he wants. That doesn't imply that he can write a 20 lines grammar that does what he wants, without doing some debugging and corrections first.
Writing grammars is a skill that just has to be learned, line any other skill too. Providing tools that make it fun and rewarding to play with parsing stuff is the best we can do.
Writing a recursive descending parser isn't hard, as you said, but it's again something that needs testing, you need put some effort into it to get good error messages from it - and why would you repeat such a task? Also you often need to write a lexer -- another burden of which Perl 6 grammars free you.
Regarding your thoughts about abstract languages: Perl 6 provides tools to make experimenting with them rather easy, which helps learning about them.
I've made the experience that a reasonably good programmer can write some 20 lines of Perl code, and it does what he wants. That doesn't imply that he can write a 20 lines grammar that does what he wants, without doing some debugging and corrections first.
Writing grammars is a skill that just has to be learned, line any other skill too. Providing tools that make it fun and rewarding to play with parsing stuff is the best we can do.