Java Package Declaration

const re = new RegExp("^\\s*package\\s+([a-z][\\w]*(?:\\.[a-z][\\w]*)*)\\s*;", "m");
const input = "package com.example.app;";
const match = input.match(re);
console.log(match ? match[0] : null);

import re

pattern = re.compile(r"^\s*package\s+([a-z][\w]*(?:\.[a-z][\w]*)*)\s*;", re.MULTILINE)
input_text = "package com.example.app;"
for m in pattern.finditer(input_text):
    print(m.group(0))

package main

import (
	"fmt"
	"regexp"
)

func main() {
	re := regexp.MustCompile(`(?m)^\s*package\s+([a-z][\w]*(?:\.[a-z][\w]*)*)\s*;`)
	input := `package com.example.app;`
	for _, match := range re.FindAllString(input, -1) {
		fmt.Println(match)
	}
}