sub convert_hex {
   my @charconv = map { pack "H*", $_ } split(/\s/, $hexval->get);

   $charval->delete(0, 'end');
   $charval->insert(0, $_) for reverse @charconv;
}

sub convert_char {
   my @hexconv = map { unpack "H*", $_ } split(//, $charval->get);

   $hexval->delete(0, 'end');
   $hexval->insert(0, $_) for reverse @hexconv;
}