I got constant strings which I typed in the script with accented chars UTF8-encoded.

If your source code is UTF-8, use use utf8;.

>perl -le"binmode STDOUT, ':encoding(iso-latin-1)'; print qq{print len
+gth '\x85'}" | perl -l
1   Good

>perl -le"binmode STDOUT, ':utf8'; print qq{print length '\x85'}" | pe
+rl -l
2   BAD!

>perl -le"binmode STDOUT, ':utf8'; print qq{use utf8; print length '\x
+85'}" | perl -l
1   Good
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