alt.addToken(RegexpConstants.DOT, 1, 1);
pattern.addAlternative(alt);
alt = new ProductionPatternAlternative();
alt.addToken(RegexpConstants.LEFT_PAREN, 1, 1);
alt.addProduction(RegexpConstants.EXPR, 1, 1);
alt.addToken(RegexpConstants.RIGHT_PAREN, 1, 1);
pattern.addAlternative(alt);
alt = new ProductionPatternAlternative();
alt.addToken(RegexpConstants.LEFT_BRACKET, 1, 1);
alt.addProduction(RegexpConstants.CHARACTER_SET, 1, 1);
alt.addToken(RegexpConstants.RIGHT_BRACKET, 1, 1);