Well, several solutions have been pointed to. Here's one I have used myself.

my(%encoding,%decoding);

sub UTF8::chr ($) {
    my $ord = shift;
    if($ord && $ord < 0x80) {
        return chr $ord;   # OR:  pack 'C', $ord;
    } elsif ($ord < 0x800) {
        return pack 'C2', 0xC0 | ($ord>>6), 0x80 | ($ord & 0x3F);
    } else {
        return pack 'C3', 0xE0 | ($ord>>12), 0x80 | (($ord>>6) & 0x3F)
+, 0x80 | ($ord & 0x3F);
    }
}

#initialize
for my $ord (0, 128 .. 256) {
    $encoding{chr $ord} = UTF8::chr($ord);
}
%decoding = reverse %encoding;

sub UTF8_to_L1 {
    foreach (@_ = @_) {
        s/(\000|[\xC0-\xDF][\x80-\xBF]|[\xE0-\xFF][\x80-\xBF][\x80-\xB
+F])/$decoding{$1} || "(#$1#)"/ge;
    }
    return wantarray ? @_ : pop;
}

sub L1_to_UTF8 {
    foreach (@_ = @_) {
        s/([\000\x80-\xFF])/$encoding{$1}/g;
    }
    return wantarray?@arg:$arg[-1];
}
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In order to make it work for 5.6 too, you need to "disarm" the UTF-8 strings in the UTF8_to_L1 sub, for example using pack('C0a*', $string)

For completeness sake, here's a sub to turn UTF-8 strings into a ordinal:

sub UTF8::ord ($) {
    my $chr = shift;
    unless ($chr =~ /^([\300-\377][\200-\277]+)/) {
        return ord $chr; # 1 byte
    }
    my @ord = unpack 'C*', $1;
    if($ord[0] & 0x20) {  # 0xE0 .. 0xFF
        return ($ord[0] & 0x1F)<<12 | ($ord[1] & 0x3F)<<6 | $ord[2] & 
+0x3F;
    } else {
        return ($ord[0] & 0x1F)<<6 | $ord[1] & 0x3F;
    }
}
[download]