NAME
Data::Random::String::Matches - Generate random strings matching a regex
SYNOPSIS
use Data::Random::String::Matches;
# Create a generator with regex and optional length
my $gen = Data::Random::String::Matches->new(qr/[A-Z]{3}\d{4}/, 7);
# Generate a matching string
my $str = $gen->generate();
print $str; # e.g., "XYZ1234"
# Alternation
my $gen2 = Data::Random::String::Matches->new(qr/(cat|dog|bird)/);
my $animal = $gen2->generate_smart(); # "cat", "dog", or "bird"
# Backreferences
my $gen3 = Data::Random::String::Matches->new(qr/(\w{3})-\1/);
my $str3 = $gen3->generate_smart(); # e.g., "abc-abc"
# Groups and quantifiers
my $gen4 = Data::Random::String::Matches->new(qr/(ha){2,4}/);
my $laugh = $gen4->generate_smart(); # "haha", "hahaha", or "hahahaha"
# Unicode
$gen = Data::Random::String::Matches->new(qr/\p{L}{5}/);
# Named captures
$gen = Data::Random::String::Matches->new(qr/(?<year>\d{4})-\k<year>/);
# Possessive
$gen = Data::Random::String::Matches->new(qr/\d++[A-Z]/);
# Lookaheads
$gen = Data::Random::String::Matches->new(qr/\d{3}(?=[A-Z])/);
# Combined
$gen = Data::Random::String::Matches->new(
qr/(?<prefix>\p{Lu}{2})\d++\k<prefix>(?=[A-Z])/
);
# Consistency with Legacy software
print Data::Random::String::Matches->create_random_string(length => 3, regex => '\d{3}'), "\n";DESCRIPTION
This module generates random strings that match a given regular expression pattern. It parses the regex pattern and intelligently builds matching strings, supporting a wide range of regex features.
SUPPORTED REGEX FEATURES
Character Classes
Basic classes:
[a-z],[A-Z],[0-9],[abc]Negated classes:
[^a-z]Ranges:
[a-zA-Z0-9]Escape sequences in classes:
[\d\w]
Escape Sequences
\d- digit [0-9]\w- word character [a-zA-Z0-9_]\s- whitespace\D- non-digit\W- non-word character\t,\n,\r- tab, newline, carriage return
Quantifiers
{n}- exactly n times{n,m}- between n and m times{n,}- n or more times+- one or more (1-5 times)*- zero or more (0-5 times)?- zero or one
Grouping and Alternation
(...)- capturing group(?:...)- non-capturing group|- alternation (e.g.,cat|dog|bird)\1,\2, etc. - backreferences
Other
.- any character (printable ASCII)Literal characters
^and$anchors (stripped during parsing)
LIMITATIONS
Lookaheads and lookbehinds ((?=...), (?!...)) are not supported
Named groups ((?<name>...)) are not supported
Possessive quantifiers (*+, ++) are not supported
Unicode properties (\p{L}, \p{N}) are not supported
Some complex nested patterns may not work correctly with smart parsing
EXAMPLES
# Email-like pattern
my $gen = Data::Random::String::Matches->new(qr/[a-z]+@[a-z]+\.com/);
# API key pattern
my $gen = Data::Random::String::Matches->new(qr/^AIza[0-9A-Za-z_-]{35}$/);
# Phone number
my $gen = Data::Random::String::Matches->new(qr/\d{3}-\d{3}-\d{4}/);
# Repeated pattern
my $gen = Data::Random::String::Matches->new(qr/(\w{4})-\1/);METHODS
new($regex, $length)
Creates a new generator. $regex can be a compiled regex (qr//) or a string. $length is optional and defaults to 10 (used for fallback generation).
generate($max_attempts)
Generates a random string matching the regex. First tries smart parsing, then falls back to brute force if needed. Tries up to $max_attempts times (default 1000) before croaking.
generate_smart()
Parses the regex and builds a matching string directly. Faster and more reliable than brute force, but may not handle all edge cases.
generate_many($count, $unique)
Generates multiple random strings matching the regex.
my @strings = $gen->generate_many(10); # 10 strings (may have duplicates)
my @strings = $gen->generate_many(10, 1); # 10 unique strings
my @strings = $gen->generate_many(10, 'unique'); # 10 unique strings
# Generate until you have 1000 unique codes
my $gen = Data::Random::String::Matches->new(qr/[A-Z]{3}\d{4}/);
my @codes = $gen->generate_many(1000, 'unique');Parameters:
$count- Number of strings to generate (required, must be positive)$unique- If true, ensures all generated strings are unique. May return fewer than$countstrings if uniqueness cannot be achieved within reasonable attempts. Accepts any true value (1, 'unique', etc.)
Returns: List of generated strings
Dies: If count is not a positive integer
Warns: If unable to generate the requested number of unique strings
get_seed()
Gets the random seed for reproducible generation
set_seed($seed)
Sets the random seed for reproducible generation
suggest_simpler_pattern()
Analyzes patterns and suggests improvements.
my $suggestion = $gen->suggest_simpler_pattern();
if ($suggestion) {
print "Reason: $suggestion->{reason}\n";
print "Better pattern: $suggestion->{pattern}\n" if $suggestion->{pattern};
print "Tips:\n";
print " - $_\n" for @{$suggestion->{tips}};
}validate($string)
Checks if a string matches the pattern without generating.
if ($gen->validate('1234')) {
print "Valid!\n";
}pattern_info()
Returns detailed information about the pattern.
my $info = $gen->pattern_info();
print "Complexity: $info->{complexity}\n";
print "Min length: $info->{min_length}\n";
print "Has Unicode: ", $info->{features}{has_unicode} ? "Yes" : "No", "\n";pattern_info analyzes a regular expression to produce a structured summary of its characteristics, including estimated string lengths, detected features, and an overall complexity rating. It first calls _estimate_length to heuristically compute the minimum and maximum possible lengths of strings matching the pattern by scanning for literals, character classes, and quantifiers. It then detects the presence of advanced regex constructions such as alternation, lookahead or lookbehind assertions, named groups, and Unicode properties, storing them in a feature hash. Finally, it calculates a rough "complexity" classification based on pattern length and detected features-returning a hash reference that describes the regex's structure, estimated lengths, and complexity level.
create_random_string
For consistency with Data::Random::String.
print Data::Random::String::Matches->create_random_string(length => 3, regex => '\d{3}'), "\n";AUTHOR
Nigel Horne, <njh at nigelhorne.com>
SEE ALSO
Test coverage report: https://nigelhorne.github.io/Data-Random-String-Matches/coverage/
LICENCE AND COPYRIGHT
Copyright 2025 Nigel Horne.
Usage is subject to licence terms.
The licence terms of this software are as follows:
Personal single user, single computer use: GPL2
All other users (including Commercial, Charity, Educational, Government) must apply in writing for a licence for use from Nigel Horne at the above e-mail.