use strict;
use warnings;

use Encode;
my $enc_flags = Encode::FB_CROAK | Encode::LEAVE_SRC;

binmode STDOUT, ':encoding(utf-8)';

while ( my $line = <> ) {
    chomp $line;

    my $decoded = eval {
        Encode::decode( 'utf-8', $line, $enc_flags );
    } || bad_string( $line );

    print $decoded, "\n";
}

sub bad_string {
    # "upgrade" the string

    Encode::decode( 'latin-1', shift );
}