$octets = encode("utf8", $string);

##</code><code>##

use Encode qw( encode );

sub string_to_literal {
   local $_ = @_ ? $_[0] : $_;
   s/(.)/
      my $o = ord($1);
      if    ($1 eq '"'              ) { '\\"'                  }
      elsif ($1 eq '\\'             ) { '\\\\'                 }
      elsif ($1 < 0x20 || $1 >= 0x7F) { sprintf('\\x{%X}', $o) }
      else                            { $1                     }
   /eg;
   return qq{"$_"};
}

sub octet_dump {
   return join ' ',
          map { sprintf('%02X', ord($_)) }
          map /(.)/g,
          @_ ? $_[0] : $_;
}

$string = "\x{03c5}";
print("\$string is ", length($string), " chars long: ");
print(string_to_literal($string), "\n");

$octets = encode("utf8", $string);
print("\$octets is ", length($octets), " bytes long: ");
print(octet_dump($octets),  "\n");

##</code><code>##

$string is 1 chars long: "\x{3C5}"
$octets is 2 bytes long: CF 85