Request for help with regexes

My Regex tests

package com.EmpowerOperations.LanguageAndLibraryTests;

import com.EmpowerOperations.Common.Ref;
import com.EmpowerOperations.LinqALike.Common.Formatting;
import com.EmpowerOperations.LinqALike.Queryable;
import org.junit.Test;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import static com.EmpowerOperations.LinqALike.Factories.from;
import static com.EmpowerOperations.LinqALike.Factories.range;

/**
 * Created by Geoff on 2014-08-06.
 */
public class RegexFixture {

    private Queryable<String> simpleNames = from("x1", "longVarName2");

    private String sourceText = "" +
            //this was taken from our sample problem, Optim.m, which is an APDL file
            "!!!! This is the kerl of optimization for sheet metal parts assembly\n" +
            "!!!!\n" +
            "\n" +
            "!!!!!!!! locator's position P1(p1x,p1y),P2(p2x,p2y)\n" +
            "!!!!!!!! Welding spot= s\n" +
            "\n" +
            "p1x=x1/1000.0\n" +
            "p1y=x2/1000.0\n" +
            "\n" +
            "p2x=x3/1000.0\n" +
            "p2y=x4/1000.0\n" +
            "\n" +
            "s=x5/1000.0\n" +
            "\n" +
            "\n" +
            "\n" +
            "/PREP7  \n" +
            "!*  \n" +
            "ET,1,SHELL63\n" +
            // manually added this line{
                "ET,MPTEMP,,,,EX, x1=38000\n" +
            // } end manual edit
            "!*  \n" +
            "!*  \n" +
            "R,1,0.001,0.001,0.001,0.001, , ,\n" +
            "RMORE, , , ,\n" +
            "RMORE   \n" +
            "RMORE, ,\n" +
            "!*  \n" +
            "!*  \n" +
            "MPTEMP,,,,,,,,  \n" +
            "MPTEMP,1,0  \n" +
            "MPDATA,EX,1,,38000*6894.75\n" +
            "MPDATA,PRXY,1,,0.3  \n" +
            "RECTNG,0,0.1,0,0.1,";

    private final String regex = " +(?<variableName>\\w+) *= *-?(?<variableValue>\\d+\\.?\\d*)";


    @Test
    public void when_scanning_using_our_regex(){
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(sourceText);

        StringBuffer output = new StringBuffer();
        int newValue = 20;

        while(matcher.find()){
            String found = matcher.group();
            int start = matcher.start();
            int end = matcher.end();
            int groupCount = matcher.groupCount();  //this does NOT return the number of groups, it returns the index of the last group!!!

            Queryable<String> groups = from(range(0, matcher.groupCount() + 1)).select(matcher::group);
            Ref<Integer> displayedIndex = new Ref<>(0);
            String groupsListed = Formatting.verticallyPrintMembers(groups.select(group -> "" + displayedIndex.target++ + ": " + group));

            System.out.println(
                    "found:'" + found + "' at " +
                    "start:" + start + " , " +
                    "end:" + end + " " +
                    "groups:" + groupCount + ", \n" +
                    "\t" + groupsListed + "\n" +
                    "near '" + sourceText.substring(Math.max(0, start - 10), Math.min(end + 10, sourceText.length() - 1)) + "'");

            String existingValue = matcher.group("variableValue");
            matcher.appendReplacement(output, "" + newValue);
        }

        matcher.appendTail(output);

        System.out.println(output.toString());

    }
}