Thanks - I overlooked that one. A brief test, with zwon's code, and it looks like it works. As long as I don't "use utf8;" or use -CS on the commandline. I'm not sure why... I suppose because the input I got wasn't actually utf8, but I don't know what else it could be when it's displaying fine here :-) (And konsole thinks that the encoding it's using is UTF-8, and LANG is set to en_US.utf8...) So I'm just confused as to why explicitly marking things as utf8 is breaking it.

I'm sure that'll be a question for the future.

For me it works with use utf8 but issues the warnings:

substr outside of string at /usr/share/perl5/Text/WrapI18N.pm line 130
+.
Use of uninitialized value $text in length at /usr/share/perl5/Text/Wr
+apI18N.pm line 52.
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Update: after investigating a bit more I also found Text::LineFold, it looks like it does the right thing, though it also ignores utf8 flag on strings.

use strict;
use warnings;
use 5.010;
use utf8;
use open ':std', ':utf8';
use Text::LineFold;

my $lf = Text::LineFold->new( ColumnsMax => 12, );
while (<>) {
    my $folded = $lf->fold($_);
    utf8::decode($folded);
    say $folded;
}
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