Does it use indentation? Does it nest them? (So that BLOCK_C would be in BLOCK_B.) Does it assume that they don't nest? (So BLOCK_C is not in BLOCK_B but "Some more code" accidentally is in BLOCK_C.) Does it depend on cues that depend on the kind of block? (So an IF might naturally terminate at an unexpected ELSE while a simple block remains open...)
It seems like a potentially confusing feature unless the rules are clear. If they are simple (eg it just assumes that when you close a named block then you close all other open blocks there) then it seems like a minor piece of syntactic sugar.
Anyways my limited understanding was that PL/I had exactly this kind of DWIMery built-in, which is why people who disliked Perl tended to likewise dislike PL/I.
Cheers,
Ben