xxx.groovy

Set<String> calledMethods = new Hashset<>()

new File(baseDir,"haiku.txt").withReader { reader ->

    while (reader.readLine()) {
        if (line.contains(') >>>>')) {
            String[] splittedLine = line.split('>>>>', 2)
            String l = splittedLine[0]
            String rest = l.substring(l.indexOf('#'))
            calledMethods.add(rest)
        }
    }
}

new File(baseDir,'haiku.txt').withWriter('utf-8') { writer ->
    calledMethods.toList().sort().each { it -> 
        writer.write(it)
    }
}