First off $9YT isn't a valid valiable name

It is if you do enough tricks.

$ perl -MData::Dumper -le '$f = "9YT"; $$f = "foo"; print Data::Dumper
+::Dumper(\%main::)'
$VAR1 = {
          # snip
          '9YT' => *{'::9YT'},
          # snip
        };
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With symbol table lookups and symbolic refs, pretty much anything is possible in a Perl variable name. I don't know of a way to get lexicals to do this, though.