code: public void execute( EnforcerRuleHelper helper )
          throws EnforcerRuleException
      {
          try
          {
              MavenProject project = (MavenProject) helper.evaluate( "${project}" );
              
              Prerequisites prerequisites = project.getPrerequisites(); 
              
              if( prerequisites == null )
              {
                  throw new EnforcerRuleException( "Requires prerequisite not set" );
              }
  
              if( mavenVersion != null )
              {
                  
                  VersionRange requiredVersionRange = VersionRange.createFromVersionSpec( mavenVersion );
                  
                  if( !requiredVersionRange.hasRestrictions() )
                  {
                      requiredVersionRange = VersionRange.createFromVersionSpec( "[" + mavenVersion + ",)" );
                  }
                  
                  VersionRange specifiedVersion = VersionRange.createFromVersionSpec( prerequisites.getMaven() );
                  
                  VersionRange restrictedVersionRange = requiredVersionRange.restrict( specifiedVersion );
                  
                  if ( restrictedVersionRange.getRecommendedVersion() == null )
                  {
                      throw new EnforcerRuleException( "The specified Maven prerequisite( " + specifiedVersion + " ) doesn't match the required version: " + mavenVersion );
                  }
              }
          }
          catch ( ExpressionEvaluationException e )
          {
              throw new EnforcerRuleException( e.getMessage(), e );
          }
          catch ( InvalidVersionSpecificationException e )
          {
              throw new EnforcerRuleException( e.getMessage(), e );
          }
      }
docs: {@inheritDoc}