What string should be used to specify encoding in Perl POD, "utf8", "UTF-8" or "utf-8"? -

it possible write perl documentation in utf-8. should write in pod:

=encoding nnn 

but should write instead nnn? different sources gives different answers.

• perlpod says that should =encoding utf8
• this stackoverflow answer states should =encoding utf-8
• and this answer tells me write =encoding utf-8

what correct answer? correct string written in pod?

=encoding utf-8 

according iana, charset names case-insensitive, utf-8 same.

utf8 perl's lax variant of utf-8. however, safety, want strict pod processors.