gulpfile.js

// load packages
var browserslist      = require('browserslist');
var gulp              = require('gulp');
var gulpAutoprefixer  = require('gulp-autoprefixer');
var gulpLess          = require('gulp-less');
var gulpMinifyCss     = require('gulp-minify-css');

// browsers for which autoprefix will add prefixes
var browsers = '> 1%, last 2 versions, IE >= 8, Firefox ESR, Opera 12.1';

gulp.task('less', function(){
  // compile less files
  gulp.src('less/main.less')
    .pipe(gulpLess())
    .pipe(gulpMinifyCss())
    .pipe(gulpAutoprefixer(browsers))
    .pipe(gulp.dest('css/'));
});

gulp.task('browserslist', function(){
  // display browsers for which autoprefix will add prefixes
  console.log(browserslist(browsers));
});

gulp.task('watch', function(){
  gulp.watch('less/**/*.less', ['less']);
});