Perl lc Function

last modified October 8, 2026

The Perl lc function converts strings to lowercase. ASCII characters are always handled as expected; for Unicode strings, lc follows Unicode case rules.

lc works with international characters. It is locale-sensitive only under use locale. It returns a new string rather than modifying the original variable.

Basic lc Usage

The simplest way to use lc is on a single string variable.

basic.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

my $text = "Hello World!";
my $lower = lc($text);

print "Original: '$text'\n";
print "Lowercase: '$lower'\n";

We demonstrate lc converting a mixed-case string to lowercase. The original string remains unchanged.

$ ./basic.pl
Original: 'Hello World!'
Lowercase: 'hello world!'

Comparing Strings Case-Insensitively

lc is useful for case-insensitive string comparisons.

compare.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

my $input = "YeS";
my $match = "yes";

if (lc($input) eq lc($match)) {
    print "Input matches (case-insensitive)\n";
} else {
    print "Input doesn't match\n";
}

This script compares user input case-insensitively by converting both strings to lowercase before comparison.

$ ./compare.pl
Input matches (case-insensitive)

Processing Arrays

lc can process array elements using map.

array.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

my @words = ("APPLE", "Banana", "CherRY");
my @lower_words = map { lc } @words;

print "Original: @words\n";
print "Lowercase: @lower_words\n";

We convert all elements of an array to lowercase. The original array remains unchanged while we create a new lowercase version.

$ ./array.pl
Original: APPLE Banana CherRY
Lowercase: apple banana cherry

International Characters

lc handles international characters correctly.

unicode.pl

#!/usr/bin/perl

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

my $text = "ÉLÉGANT Zürich";
my $lower = lc($text);

binmode STDOUT, ':utf8';
print "Original: '$text'\n";
print "Lowercase: '$lower'\n";

This demonstrates lc working with accented characters and umlauts. Note the use utf8 pragma for Unicode support.

$ ./unicode.pl
Original: 'ÉLÉGANT Zürich'
Lowercase: 'élégant zürich'

lc vs lcfirst

lc differs from lcfirst which only affects the first character.

compare_functions.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

my $text = "Perl Programming";

print "lc: ", lc($text), "\n";
print "lcfirst: ", lcfirst($text), "\n";

lc converts the entire string while lcfirst only changes the first character to lowercase.

$ ./compare_functions.pl
lc: perl programming
lcfirst: perl Programming

Using with Hashes

lc can normalize hash keys for case-insensitive lookups.

hash.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;

my %colors = (
    red => "#FF0000",
    green => "#00FF00",
    blue => "#0000FF"
);

my $user_input = "RED";
my $color_code = $colors{lc $user_input};

if (defined $color_code) {
    print "Hex code for $user_input is $color_code\n";
} else {
    print "Color not found\n";
}

We use lc to normalize user input before hash lookup. This allows case-insensitive access to hash values.

$ ./hash.pl
Hex code for RED is #FF0000

Locale Awareness

Under use locale, lc uses the current locale settings for case conversion.

locale.pl

#!/usr/bin/perl

use strict;
use warnings;
use v5.34.0;
use utf8;
use locale;
use POSIX qw(locale_h);

binmode STDOUT, ':utf8';
my $text = "İSTANBUL";

setlocale(LC_ALL, 'tr_TR.UTF-8');
print "Turkish locale: ", lc($text), "\n";

setlocale(LC_ALL, 'en_US.UTF-8');
print "English locale: ", lc($text), "\n";

This shows how locale affects lowercase conversion, particularly with Turkish dotted/dotless I. Note: Locale must be available on your system.

$ ./locale.pl
Turkish locale: i̇stanbul
English locale: i̇stanbul

Best Practices

Use for normalization: Standardize strings before comparison.
Combine with chomp: Clean input with both functions.
Consider Unicode: Ensure proper encoding for non-ASCII.
Performance: Avoid unnecessary conversions in loops.

Source

Perl lc Documentation

This tutorial covered Perl's lc function with practical examples demonstrating its usage in various scenarios.

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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