Subnet CIDR IPv4

<?php
// PHP 8.2+ (PCRE)
$pattern = '~^(?:(?:25[0-5]|2[0-4]\d|1?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|1?\d?\d)\/(?:[0-9]|[12]\d|3[0-2])$~';
$isValid = (bool) preg_match($pattern, $text);

// Estrazione con gruppi
if (preg_match($pattern, $text, $matches)) {
    print_r($matches);
}

# Python 3 (re)
import re

pattern = r"^(?:(?:25[0-5]|2[0-4]\d|1?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|1?\d?\d)\/(?:[0-9]|[12]\d|3[0-2])$"
is_valid = bool(re.search(pattern, text))

# Estrazione match
match = re.search(pattern, text)
if match:
    print(match.group(0))

// Go (regexp)
package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`^(?:(?:25[0-5]|2[0-4]\d|1?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|1?\d?\d)\/(?:[0-9]|[12]\d|3[0-2])$`)
	isValid := re.MatchString(text)
	fmt.Println(isValid)
}

// C# (.NET)
using System;
using System.Text.RegularExpressions;

bool isValid = Regex.IsMatch(text, @"^(?:(?:25[0-5]|2[0-4]\d|1?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|1?\d?\d)\/(?:[0-9]|[12]\d|3[0-2])$");