use strict;

use Encode;

# my raw data
my $data = "\xe0\xe1\x02\n";
# interpret it as text in encoding CP1251
my $txt = Encode::decode("cp1251", $data);

# convert text to octets in encoding Latin1.
# Replace bad ones with X
my $nd = Encode::encode("latin1", $txt, sub{ return "X" });

# just to see the result in the terminal which uses UTF-8 encoding
Encode::from_to($nd, "latin1", "UTF-8");
print $nd, "\n"