title: Possible bug when parsing properties with goal "regex-property" of build-helper-maven-plugin?
body: <p>The requirement is that I have to parse a system property with regex in order to remove the dot from the value.</p>
  
  <p>Execution example is: mvn install -Dsomeversion=1.3</p>
  
  <p>pom.xml configuration is:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;plugin&gt;
   &lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
   &lt;artifactId&gt;build-helper-maven-plugin&lt;/artifactId&gt;
   &lt;version&gt;1.8&lt;/version&gt;
   &lt;executions&gt;
    &lt;execution&gt;
     &lt;id&gt;regex-property&lt;/id&gt;
     &lt;goals&gt;
      &lt;goal&gt;regex-property&lt;/goal&gt;
     &lt;/goals&gt;
     &lt;configuration&gt;
      &lt;name&gt;someversion.parsed&lt;/name&gt;
      &lt;value&gt;$\{someversion}&lt;/value&gt;
      &lt;regex&gt;(.*)[\._](.*)&lt;/regex&gt;
      &lt;replacement&gt;$1$2&lt;/replacement&gt;
      &lt;failIfNoMatch&gt;false&lt;/failIfNoMatch&gt;
     &lt;/configuration&gt;
    &lt;/execution&gt;
   &lt;/executions&gt;
  &lt;/plugin&gt;
  </code></pre>
  
  <p>Based on the plugin's documentation, the backslash must be there after the dollar sign in <code>&lt;value&gt;</code></p>
  
  <p>The issues are:</p>
  
  <ol>
  <li>When the backslash is there, the system property is not parsed</li>
  <li>If I remove the backslash:<br/>
  a) system property is parsed successfully<br/>
  b) if execute "mvn install" I am getting the error that the parameter 'value' is
     missing or incorrect, despite the fact that I have configured <code>&lt;failIfNoMatch&gt;false&lt;/failIfNoMatch&gt;</code></li>
  </ol>
  
  <p>Any feedback would be highly appreciated</p>
  
  <p>Thank you in advance</p>