import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
 
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String [] arr = {"${US.IDX_CA}", "${UK.IDX_IO}", "${NZ.IDX_BO}", "${JP.IDX_TK}", "${US.IDX_MT}", "more-elements-with-completely-different-patterns-which-is-irrelevant"};
		Pattern pattern = Pattern.compile("\\bIDX_(\\w{2})\\b");
		for (String s : arr){
		     Matcher m = pattern.matcher(s);
		      while (m.find()){
		        System.out.println(m.group(0)); // Get the whole match
        		System.out.println(m.group(1)); // Get the 2 chars after IDX_
		      }
		}
	}
}

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