less-plugin-autoprefix plugin with Gulp showing error - less

Question

The less-plugin-autoprefixer plugin README says that, to use the plugin, you include this in your gulpfile.js:
var LessPluginAutoPrefix = require('less-plugin-autoprefix'),
autoprefixPlugin = new LessPluginAutoPrefix({browsers: ["last 2 versions"]});
less.render(lessString, { plugins: [autoprefixPlugin] })
.then(
Do they want me to put an open ended callback function here? I'm confused. I tried including just the first part:
var LessPluginAutoPrefix = require('less-plugin-autoprefix'),
autoprefixPlugin = new LessPluginAutoPrefix({browsers: ["last 2 versions"]});
and then called the plugin like this:
gulp.task('less', ['clean'], function() {
return gulp.src('app.less')
.pipe(less({
includePaths: ['less'],
plugins: [autoprefixPlugin] //***//
}))
.pipe(cssmin({keepSpecialComments: 0}))
.pipe(rename('app.full.min.css'))
.pipe(gulp.dest('../server/dist/'))
.pipe(filter('../server/dist/**/*.css'))
.pipe(reload({stream:true}));
});
But I receive the following error:
TypeError: Object #<Autoprefixer> has no method 'on'
at DestroyableTransform.Stream.pipe (stream.js:65:8)
at Gulp.<anonymous> (/Users/himmel/Sites/matt-mcdaniel.com/client/gulpfile.js:131:10)
I've included the necessary dependency, autoprefixer-core, what am I missing here?

Answer 1

The error was thrown for an unknown reason due to inclusion of:
var autoprefixer = require('autoprefixer-core');
After removing this, no error was thrown.
Additionally, including:
var LessPluginAutoPrefix = require('less-plugin-autoprefix'),
autoprefixPlugin = new LessPluginAutoPrefix({browsers: ["last 2 versions"]});
and
gulp.task('less', ['clean'], function() {
return gulp.src('app.less')
.pipe(less({
includePaths: ['less'],
plugins: [autoprefixPlugin] //***//
}))
.pipe(cssmin({keepSpecialComments: 0}))
.pipe(rename('app.full.min.css'))
.pipe(gulp.dest('../server/dist/'))
.pipe(filter('../server/dist/**/*.css'))
.pipe(reload({stream:true}));
});
was sufficient for my gulpfile to autoprefix on build, but did not autoprefix via BrowserSync during development.