Groovy DSL example: Better Bouquet, see https://sandstorm.de/de/blog/post/how-to-create-a-dsl-with-groovy.html

BetterBouquetDsl.groovy

// our configuration model
class BouquetConfiguration extends ArrayList<String> {
    
    int howMany(String flower) {
        return this.count { it == flower }
    }
    
    String toString() {
        return "Bouquet: " + this.toString()
    }
}

// our DSL keyword
class BouquetConfigurationDsl {
    private final BouquetConfiguration bouquet
    
    BouquetConfigurationDsl(BouquetConfiguration bouquet) {
        this.bouquet = bouquet
    }
    
    void flower(String flower) {
        bouquet << flower
    }
}

class Bouquet {
    static BouquetConfiguration create(
        @DelegatesTo(strategy = Closure.DELEGATE_FIRST, value = BouquetConfigurationDsl) Closure script
    ) {
        def bouquet = new BouquetConfiguration()
        script.resolveStrategy = Closure.DELEGATE_FIRST
        script.delegate = new BouquetConfigurationDsl(bouquet)
        script()
        return bouquet
    }
}

def bouquet = Bouquet.create {
    flower "cornflower"
    flower "cornflower"
    flower "poppy"
    flower "calendula"
}

println bouquet