/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
 
		String str = "someText\n\nbegin\n  .someMethod()\n  .doSomething(TOKEN_123)\n  .someMethod()\nend\n\nbegin\n  .someMethod()\n  .doSomething(TOKEN_456)\n  .someMethod()\nend\n\nbegin\n  .someMethod()\n  .doSomething(TOKEN_789)\n  .someMethod()\nend\n\nmore Text"; 
		System.out.println(str.replaceFirst("(?s)begin(?:(?!begin).)*TOKEN_456.*?end\\s*", ""));
 
	}
}

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