Note that can be warned on implicit utf8 upgrade

The module encoding::warnings can be used to warn when two strings are
concatenated where one is utf8 and the other is not and contains
non-ASCII.

Note the existence of this in the pod documentation.

diff --git a/pod/perlunicode.pod b/pod/perlunicode.pod
index ae13a33..1f4be43 100644 (file)
--- a/pod/perlunicode.pod
+++ b/pod/perlunicode.pod
@@ -122,7 +122,8 @@ be used to force byte semantics on Unicode data, and the C<use feature
 
 If strings operating under byte semantics and strings with Unicode
 character data are concatenated, the new string will have
-character semantics.  This can cause surprises: See L</BUGS>, below
+character semantics.  This can cause surprises: See L</BUGS>, below.
+You can choose to be warned when this happens.  See L<encoding::warnings>.
 
 Under character semantics, many operations that formerly operated on
 bytes now operate on characters. A character in Perl is