Perl hex Function
last modified April 4, 2025
The Perl hex function converts hexadecimal strings to decimal
numbers. It interprets a string as a hex number and returns its decimal
equivalent.
hex is useful when working with hexadecimal values from files,
user input, or network protocols. It handles both uppercase and lowercase
hex digits (A-F or a-f).
Basic hex Usage
The simplest way to use hex is with a hexadecimal string.
#!/usr/bin/perl use strict; use warnings; use v5.34.0; my $hex_value = "FF"; my $decimal = hex($hex_value); print "Hexadecimal $hex_value is decimal $decimal\n";
We convert the hexadecimal string "FF" to its decimal equivalent. The function returns 255, which is FF in base 16.
$ ./basic.pl Hexadecimal FF is decimal 255
Hexadecimal Prefix Handling
hex automatically ignores the common "0x" prefix.
#!/usr/bin/perl use strict; use warnings; use v5.34.0; my $hex1 = "0xFF"; my $hex2 = "FF"; print "With prefix: ", hex($hex1), "\n"; print "Without prefix: ", hex($hex2), "\n";
Both forms produce the same result. The function skips leading whitespace and the "0x" prefix if present.
$ ./prefix.pl With prefix: 255 Without prefix: 255
Case Insensitivity
hex works with both uppercase and lowercase hex digits.
#!/usr/bin/perl use strict; use warnings; use v5.34.0; my $upper = "ABCD"; my $lower = "abcd"; print "Uppercase: ", hex($upper), "\n"; print "Lowercase: ", hex($lower), "\n";
The function treats 'A' and 'a' identically, converting both to decimal 43981. This makes it flexible with different input formats.
$ ./case.pl Uppercase: 43981 Lowercase: 43981
Invalid Characters
hex stops conversion at the first invalid character.
#!/usr/bin/perl use strict; use warnings; use v5.34.0; my $valid = "1A3F"; my $invalid = "1G3F"; print "Valid: ", hex($valid), "\n"; print "Invalid: ", hex($invalid), "\n";
The function converts "1G3F" as just "1" since 'G' isn't a hex digit. No warning is issued for invalid characters.
$ ./invalid.pl Valid: 6719 Invalid: 1
Hexadecimal to Binary
Combine hex with sprintf for binary conversion.
#!/usr/bin/perl
use strict;
use warnings;
use v5.34.0;
my $hex = "A5";
my $decimal = hex($hex);
my $binary = sprintf("%08b", $decimal);
print "Hex $hex is binary $binary\n";
We first convert to decimal, then format as 8-bit binary. The %08b
format ensures leading zeros for consistent 8-digit output.
$ ./binary.pl Hex A5 is binary 10100101
Reading Hex from File
hex is useful when processing hexadecimal data from files.
#!/usr/bin/perl
use strict;
use warnings;
use v5.34.0;
open(my $fh, '<', 'hexdata.txt') or die "Can't open file: $!";
while (my $line = <$fh>) {
chomp $line;
print "$line = ", hex($line), "\n";
}
close($fh);
This script reads hex values from a file and converts each to decimal.
The chomp removes newlines before conversion.
Hexadecimal Arithmetic
hex enables arithmetic operations on hex strings.
#!/usr/bin/perl
use strict;
use warnings;
use v5.34.0;
my $hex1 = "A";
my $hex2 = "5";
my $sum = hex($hex1) + hex($hex2);
print "$hex1 + $hex2 = $sum (decimal)\n";
my $hex_sum = sprintf("%X", $sum);
print "Sum in hex: $hex_sum\n";
We convert hex strings to decimal, perform addition, then format the result back to hexadecimal. This demonstrates complete hex/decimal conversion.
$ ./arithmetic.pl A + 5 = 15 (decimal) Sum in hex: F
Best Practices
- Validate input: Check strings contain valid hex digits.
- Handle case: Accept both uppercase and lowercase.
- Watch for overflow: Perl handles big integers well.
- Combine with sprintf: For flexible output formatting.
Source
This tutorial covered Perl's hex function with practical
examples demonstrating hexadecimal to decimal conversion.
Author
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