Two syntax forms are available for Perl hex function:

hex EXPR 
hex

• has as argument a hexadecimal string (or an expression which after evaluation will return a hex string)
• will return the decimal corresponding value

print hex "0x4E8", "\n";  # or
print hex "4e8", "\n";

In the second syntax form of Perl hex function, the expression argument is omitted and the function will use by default as argument the hexadecimal value stored in the special variable $_.

Next, I’ll give you some examples about how you can use and manipulate Perl hex function and some related considerations.

# initialize a scalar variable with an integer value
my $dec = 1211;

print "Hexadecimal number: ", uc(sprintf("%x\n", $dec)), "\n";
# displays 4BB

This is a direct conversion method when we need to use a reverse function for Perl hex function. If you want to write some code and emulate the algorithm used by sprintf formatting, here is an example:

# initialize a scalar with an integer value
my $dec = 1211;

# call the subroutine
my $hex = DecToNumBase($dec, 16);
print "Hexadecimal number: $hex\n";
# displays 4BB

# define the subroutine
sub DecToNumBase
{
  my $decNumber = $_[0];
  my $numBase = $_[1];
  my $numNumber = '';

  while($decNumber ne 'end') 
  {
    # divide the decimal number by $numBase and 
    # store the remainder (modulus function) in 
    # the temporary variable $temp
    my $temp = $decNumber % $numBase;
    if($temp > 9) 
    {
      $temp = chr($temp + 55);
    }
    $numNumber = $temp . $numNumber;
    $decNumber = int($decNumber / $numBase);
    if($decNumber < $numBase) 
    {
      if($decNumber > 9) 
      {
        $decNumber = chr($decNumber + 55);
      }
      $numNumber = $decNumber . $numNumber;
      $decNumber = 'end'; 
    } 
  }
  return $numNumber;
}

In the example above we defined and called the DecToNumBase subroutine which is meant to convert a decimal value into a number in another numeration base. This subroutine has as input two arguments:

• the decimal value to be converted
• the numeration base

my $myString="This text is only for test reason 123 [{@!}}|";

my @myArray=unpack('C*', $myString);
my $myStringHex = '';

foreach my $c (@myArray) {
  $myStringHex .= "\%" . sprintf ("%lx", $c);
}

print "$myStringHex\n";

Everyone who is searching through Internet knows about URL (or more precisely, he should know). Let’s say that through URL we understand an internet address of a page we are searching for, it could be the address of this page too (URL=http://www.misc-perl-info.com/perl-hex.html).

There are some restrictions of using the characters in an URL. Through the characters allowed there are the alphanumerical characters [0-9a-zA-Z], some punctuation symbols $-_.!*'(), and some reserved characters used for other purposes.

All the other characters must be encoded, because they could be misunderstood if they are found within an URL. To encode a character means to replace it by the symbol % followed by its two-digit hexadecimal code. For instance, the space character which has the hexadecimal code 20, will be represented as %20.

The simplest mode to encode or decode an URL is by using the Perl URI::Escape module, which exports the following functions:

• uri_escape – which replaces (encodes) all unsafe characters within a URL string with two hexadecimal digits preceded by the % symbol
• uri_unescape – which unencodes all the characters within an URL, i.e replaces any occurrence of % followed by two hexadecimal digits into their corresponding character (in other words converts an encoded URL to its normal representation)

use URI::Escape;
 
# Encode URL
my $url = "http://www.google.com/search?q=book";

my $encodedURL = uri_escape($url);
 
print "Encoded URL: $encodedURL\n\n";

# Decode URL

$encodedURL = 
  "http://%77%77%77%2e%79%61%68%6f%6f%2e%63%6f%6d";

my $decodedURL = uri_unescape($encodedURL);
print  "Decoded URL: $decodedURL\n";

The uri_unescape function is very useful if you will receive an invitation to click on a link with escaped characters that looks like "http://%77%77%77%2e%79%61%68%6f%6f%2e%63%6f%6d" and it will be nice to know where you will go if you click on it. Decode it like in the example above and than decide what you will do. If you want to see what URL represents the above address, just copy the string above (neglect the quotes) in your browser address bar and see where it is pointing out (in my 3.0.6 FireFox it works).

We hope that these considerations help you see how to use Perl hex function in your scripts. If you have any idea to add some more useful examples about Perl hex function, feel free to tell me by using my contact form.

If you want to download the Perl hex script with all the above examples included, please click here: Script download