Grunt Autoprefixer plugin usage syntax

autoprefixer-example.scss

/*
  Autoprefixer
  https://github.com/nDmitry/grunt-autoprefixer
  Adds vendor prefixes automatically
  https://github.com/nDmitry/grunt-autoprefixer
*/

autoprefixer: {
  options: {
	  browsers: [
	    'last 2 version',
	    'safari 6',
	    'ie 8',
	    'opera 12.1',
	    'ios 6',
	    'android 4'
    ]
  },
  dev: {
	  files: {
	    '<%= project.src %>/css/style.min.css': ['<%= project.src %>/css/style.unprefixed.css'],
	    '<%= project.src %>/css/old-ie.min.css': ['<%= project.src %>/css/old-ie.unprefixed.css']
	  }
  },
	dist: {
	  files: {
	    '<%= project.src %>/css/style.prefixed.css': ['<%= project.src %>/css/style.unprefixed.css'],
	    '<%= project.src %>/css/old-ie.prefixed.css': ['<%= project.src %>/css/old-ie.unprefixed.css']
	  }
  }
}