So far I don't understand this :

 sub attempt_closure_after_successful_candidate_file_open
      (&closure, @fileList)
    {
        foreach my $file (@fileList) {
            my $f is post { close }
                = try { open $file or die; CATCH { next } }
            &closure($f);
            return;
        }
        throw Exception "Can't open any file.",
               debug => @fileList . " tried.";
    }
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This is supposed to be easier to read??

On the other hand, I like

   my $foo = BEGIN{ compute_cont() } + $foobar;
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That's cool :-) Although, I guess if you're going to do these compile-time evaluations, it would be nicer if you could do some sort of C-macro-substitution type of thing using arbitrary symbols, so that you don't have to repeat these BEGIN{} blocks.