How do I find out which encoding a filehandle is using

Sorry, this may be a totally obvious question, but I've looked hard at 
the docs...
How do I find which encoding a filehandle is using. I know I can do:

open (my $fh,"<:encoding(EUC-JP)","fred");

say, but is there a way I can tell (say) EUC-JP if I've been given $fh?

David