"I think if you want to change STDOUT globally for the debugger, some of the unicode flags in perlrun should do. (untested)"

I tried all of these:

$ perl -C -de1
...

$ perl -de1
...
  DB<1> use open OUT => qw{:encoding(UTF-8) :std}
...


$ perl -Mopen=OUT,:encoding\(UTF-8\),:std -de1
...
[download]

All gave the "Wide character ..." warning. All still printed "☺". There's probably other avenues of investigation for a global change: I didn't try anything further.