Decimal 2 Hexadecimal

Here are two ways to convert from decimal to hexadecimal.

Using sprint

$DEC = 32043;

$HEX =  sprintf ("%X", $DEC);

print "$DEC decimal equals to $HEX hexadecimal \n";

Using unpack

$string="One OS to rule them all, One OS to find them, One OS to bring them all and in the darkness bind them.";

$out = unpack("H*",$string);

print "The string in HEX \n";

print "$out\n";

So, now how to convert back form hexadecimal to decimal?