So, where's the requirement that both the proto and the definition have the same signature? It's trivial to write BNF for a proto, it's trivial BNF for the definition (given the BNF for the block). It's impossible to use BNF for the requirement that the signatures (that is, name and prototype) are the same.

Your BNF is ok if you're allowed to write: 

sub hello($);
sub hello() {print("Hello, world");}

[download]
But you aren't. The signatures should be the same - and that's unexpressable with BNF.

In reply to Re^3: Perl not BNF-able?? by Anonymous Monk
in thread Perl not BNF-able?? by anonymized user 468275

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