Perl ord Function

last modified April 4, 2025

The Perl ord function returns the numeric ASCII or Unicode value of the first character of a string. It's essential for character encoding.

ord is the inverse of chr, which converts numbers to characters. It works with both ASCII and Unicode characters in Perl.

Basic ord Usage

The simplest way to use ord is on a single character string.

basic.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

my $char = 'A';
my $code = ord($char);

print "The ASCII code of '$char' is $code\n";

We demonstrate ord converting a character to its ASCII value. The function returns the numeric code point of the first character.

$ ./basic.pl
The ASCII code of 'A' is 65

Working with Unicode

ord handles Unicode characters beyond ASCII range.

unicode.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;
use utf8;

my $char = '€';
my $code = ord($char);

print "The Unicode code point of '$char' is U+", sprintf("%04X", $code), "\n";

This script shows ord working with a Unicode Euro symbol. We format the output as a hexadecimal Unicode code point.

$ ./unicode.pl
The Unicode code point of '€' is U+20AC

Multiple Characters

ord only processes the first character of multi-character strings.

multichar.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

my $text = 'Perl';
my $code = ord($text);

print "The code of first character in '$text' is $code\n";
print "First character is '", chr($code), "'\n";

When given a longer string, ord only examines the first character. We use chr to demonstrate the reverse conversion.

$ ./multichar.pl
The code of first character in 'Perl' is 80
First character is 'P'

Comparing Characters

ord is useful for character comparisons and sorting.

compare.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

my @chars = ('z', 'a', 'M', '9', '!');
my @sorted = sort { ord($a) <=> ord($b) } @chars;

print "Original: @chars\n";
print "Sorted by code: @sorted\n";

We sort characters by their ASCII values using ord. This shows the numeric ordering of different character types.

$ ./compare.pl
Original: z a M 9 !
Sorted by code: ! 9 M a z

Character Case Conversion

ord can help implement custom case conversion logic.

case.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

sub to_upper {
    my $char = shift;
    my $code = ord($char);
    
    return $code >= 97 && $code <= 122 ? 
        chr($code - 32) : $char;
}

my $lower = 'h';
my $upper = to_upper($lower);

print "'$lower' in uppercase is '$upper'\n";

This example demonstrates using ord to check ASCII values for lowercase letters and convert them to uppercase by adjusting the code.

$ ./case.pl
'h' in uppercase is 'H'

Validating Input

ord can validate character ranges in user input.

validate.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

print "Enter a digit (0-9): ";
my $input = <STDIN>;
chomp $input;

my $code = ord($input);

if (length($input) == 1 && $code >= 48 && $code <= 57) {
    print "Valid digit entered: $input\n";
} else {
    print "Invalid input. Please enter a single digit.\n";
}

We use ord to verify the input is a single ASCII digit by checking its code point falls within the digit range (48-57).

$ ./validate.pl
Enter a digit (0-9): 5
Valid digit entered: 5

Creating Character Tables

ord helps generate character code tables.

table.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

print "ASCII Table (32-126):\n";
print "Dec Hex Char\n";

for my $i (32..126) {
    my $char = chr($i);
    printf "%3d %02X  %s\n", $i, $i, $char eq ' ' ? 'SPACE' : $char;
}

This script generates an ASCII table using both ord and chr. It displays decimal, hexadecimal, and character values.

$ ./table.pl
ASCII Table (32-126):
Dec Hex Char
 32 20  SPACE
 33 21  !
 34 22  "
...
126 7E  ~

Best Practices

Understand encoding: Know if you're working with ASCII or Unicode.
Check string length: ord only processes first character.
Use with chr: Combine with chr for conversions.
Document ranges: Comment numeric ranges for readability.

Source

Perl ord Documentation

This tutorial covered Perl's ord function with practical examples demonstrating character to code point conversion.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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