$ perl -e " print chr(999) "
Wide character in print at -e line 1.
ϧ
$ perl -e " binmode STDOUT; print chr(999) "
Wide character in print at -e line 1.
ϧ
$ perl -Mdiagnostics -e " print chr(999) "
Wide character in print at -e line 1 (#1)
(S utf8) Perl met a wide character (>255) when it wasn't expecting
one. This warning is by default on for I/O (like print). The easiest
way to quiet this warning is simply to add the :utf8 layer to the
output, e.g. binmode STDOUT, ':utf8'. Another way to turn off the
warning is to add no warnings 'utf8'; but that is often closer to
cheating. In general, you are supposed to explicitly mark the
filehandle with an encoding, see open and perlfunc/binmode.
ϧ
####
$ perl -e " no warnings q[utf8]; print chr(999) "
ϧ
##
##
$ perl -e " use bytes; print chr(999) "
τ