$str="0x123456789ABCDE Tom...";
print "$str\n";

$bytes=unpack("H*",$str); # hex string 
print "$bytes\n";

$str2 = pack("H*", $bytes);
print "$str2\n";

$bytes = unpack("h*",$str); # hex string

print "$bytes\n";

$str1 = pack("h*", $bytes);
print"$str1\n";