How do I sanitize invalid UTF-8 in Perl?

Question

My Perl program takes some text from a disk file as input, wraps it in some XML, then outputs it to STDOUT. The input is nominally UTF-8, but sometimes has junk inserted. I

Answer 1

You have a utf8 string containing some invalid utf8...

This replaces it with a default 'bad char'.

use Encode qw(decode encode);

my $octets    = decode('UTF-8', $malformed_utf8, Encode::FB_DEFAULT);

my $good_utf8 = encode('UTF-8', $octets,         Encode::FB_CROAK);