ReferenceSearch.INSTANCE.registerExecutor(new CustomReferenceSearcher());

/**
 * @author max
 */
public class CustomReferencesSearcher implements QueryExecutor<PsiReference, ReferencesSearch.SearchParameters> {
  public boolean execute(final ReferencesSearch.SearchParameters params, final Processor<PsiReference> consumer) {
    final PsiElement target = params.getElementToSearch();
    final SearchScope searchScope = limitToFileType(params.getScope(), StdFileTypes.XML); // Your custom language file type here

    if (target instanceof PsiMethod) {
      String name = ((PsiMethod)target).getName();
      if (name.startsWith("xxx")) {
        String searchText = "yyy" + name.substring(3);
        final TextOccurenceProcessor processor = new TextOccurenceProcessor() {
          public boolean execute(PsiElement element, int offsetInElement) {
            final PsiReference[] refs = element.getReferences();
            for (PsiReference ref : refs) {
              if (ref.getRangeInElement().contains(offsetInElement)) {
                if (ref.isReferenceTo(target)) {
                  return consumer.process(ref);
                }
              }
            }
            return true;
          }
        };
        
        return PsiManager.getInstance(target.getProject()).getSearchHelper().processElementsWithWord(processor, searchScope, searchText, UsageSearchContext.IN_CODE, true);
      }
    }

    return true;
  }

  private static SearchScope limitToFileType(SearchScope scope, final FileType type) {
    return scope.intersectWith(new GlobalSearchScope() {
      public boolean contains(VirtualFile file) {
        return file.getFileType() == type;
      }

      public int compare(VirtualFile file1, VirtualFile file2) {
        return 0; // irrelevant
      }

      public boolean isSearchInModuleContent(Module aModule) {
        return true;
      }

      public boolean isSearchInLibraries() {
        return false;
      }
    });
  }
}