code: public boolean parse(Context context, ProcPatternElement terminator) {
          Source source = context.getSource();
          int offset = source.getOffset();
  
          int end;
          if (terminator != null && !ghost) {
              end = terminator.findIn(source);
              if (end < 0) {
                  if (regex == null) {
                      return false;
                  } else {
                      end = source.length();
                  }
              }
          } else {
              end = source.length();
          }
  
  
          CharSequence value = source.sub(end);
  
          // If define regex, then find this regex in value
          if (regex != null) {
              Matcher matcher = regex.matcher(value);
              if (matcher.lookingAt()) {
                  int lend = matcher.end();
                  end = offset + lend;
                  value = matcher.group();
              } else {
                  return false;
              }
          }
  
          // Old context value
          CharSequence old = (CharSequence) context.getAttribute(getName());
  
          // Test this variable already defined and equals with this in this code scope
          CharSequence attr = (CharSequence) context.getLocalAttribute(getName());
          if (attr == null || attr.equals(value)) {
              if (attr == null) {
                  if (action == Action.rewrite) {
                      setAttribute(context, value);
                  } else {
                      /* action == append */
                      if (old != null) {
                          setAttribute(context, new StringBuilder().append(old).append(value));
                      } else {
                          setAttribute(context, value);
                      }
                  }
              }
              if (!ghost) {
                  source.incOffset(end - offset);
              }
              return true;
          } else {
              return false;
          }
      }
docs: Парсит элемент
  
  @param context контекст
  @return true - если удалось распарсить константу
  false - если не удалось