Gulp pipe in a loop out to multiple destinations

I am trying to run a gulp task I have to compile my less files with some extra functionality. I want when a --production flag is passed it then .pipes the results to various destination according to an array of languages that where set earlier. I currently have it working but there is alot of overhead because it compiles and run uncss each time.

Currently

From the js

lang.forEach(o => {
    if (shell.exec("npm run less -- --production --lang " + o).code) {
          shell.echo(red('Less css compile error'));
          shell.exit(1);
    }
})

then the gulp file

gulp.task 'less', ->
    gulp.src(cssSrc)
    .pipe(logger(
        before: 'Compiling less files ...'
        after: 'Less files compiled'
        showChange: true))
    .pipe(less()
    .on('error', gutil.log)
    .on('error', gutil.beep)
    .on('error', (err) ->
        pathToFile = err.fileName.split('\\')
        file = pathToFile[pathToFile.length - 1]
        return
    ))
    .pipe(minifyCSS())
    .pipe(rename('styles.min.css'))
    .pipe(gulpif(argv.production, uncss(unCssOptions)))
    .pipe gulp.dest('public/' + argv.lang + '/assets/css' )
    return

This is does not work to well either because if I dont run production flag mode it creates a undefined folder.

If someone would car to educate me on this would be great.

Thank

via Alex Kirwan