$ perl -Mdiagnostics -Mstrict -e " my $f = 'asdf'; $$f{3}++;
Can't use string ("asdf") as a HASH ref while "strict refs" in use at -e line 1 (#1)
    (F) Only hard references are allowed by "strict refs".  Symbolic
    references are disallowed.  See perlref.

Uncaught exception from user code:
        Can't use string ("asdf") as a HASH ref while "strict refs" in use at -e line 1.
 at -e line 1