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<?php
// PHP 8.2+ (PCRE)
$pattern = '~^[a-fA-F0-9]{64}$~';
$isValid = (bool) preg_match($pattern, $text);

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

# Python 3 (re)
import re

pattern = r"^[a-fA-F0-9]{64}$"
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(`^[a-fA-F0-9]{64}$`)
	isValid := re.MatchString(text)
	fmt.Println(isValid)
}

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

bool isValid = Regex.IsMatch(text, @"^[a-fA-F0-9]{64}$");