Yikes! If you're going to use eval do a better job of converting your strings to literals!

Better yet, don't use eval at all.

my %finish;
for my $indexes (@start) {
   my $p = \\%finish;
   $p = \($$p->{$_}) for @$indexes;
   $$p = 1;
}
[download]

Data::Diver hides that mess away.