Gruntfile.js

/* jshint undef: true, unused: true */
/* global module */

module.exports = function(grunt) {
  require('time-grunt')(grunt);

  grunt.initConfig({ // task definitions below

    // Compile LESS to css.
    less: {
      test: {
        files: [
          {
            src: 'main.less',
            dest: 'compiled.css'
          }
        ]
      }
    },

    replace: {
      test: {
        overwrite: true,
        options: {
          patterns: [
            {
              match: '../src1',
              replacement: 'string replaced!'
            },
            {
              match: '../src2',
              replacement: 'string replaced!'
            }
          ],
          force: true,
          usePrefix: false
        },
        files: {
          'compiled.css': 'compiled.css'
        }
      }
    }

  });

  /*
  Leaving all dependencies to track down possible conflicts
   */
  grunt.loadNpmTasks('grunt-contrib-requirejs');
  grunt.loadNpmTasks('grunt-contrib-jshint');
  grunt.loadNpmTasks('grunt-contrib-cssmin');
  grunt.loadNpmTasks('grunt-contrib-concat');
  grunt.loadNpmTasks('grunt-contrib-watch');
  grunt.loadNpmTasks('grunt-contrib-clean');
  grunt.loadNpmTasks('grunt-contrib-copy');
  grunt.loadNpmTasks('grunt-text-replace');
  grunt.loadNpmTasks('grunt-fileindex');
  grunt.loadNpmTasks('assemble-less');
  grunt.loadNpmTasks('grunt-ssh');
  grunt.loadNpmTasks('grunt-concurrent');

  // *** DEFAULT ***
  grunt.registerTask(
    'default', [
      'test'
    ]
  );

  grunt.registerTask(
    'test', [
      'less:test',
      'replace:test'
    ]
  );


};

main.less

/* src1 */
@import (less) "src1.less";

/* src2 */
@import (less) "src2.less";

.main {
  background-image: url(../dummy.png);
}

package.json

{
  "name": "grunt-replace-test",
  "description": "A test case for grunt-replace",
  "author": "Piotr Zaborowski <zamber88@gmail.com>",
  "repository": {
    "type": "git",
    "url": "https://gist.github.com/9969919.git"
  },
  "devDependencies": {
    "nunjucks": "~0.1.10",
    "grunt": "~0.4.1",
    "grunt-contrib-jshint": "~0.6.0",
    "grunt-contrib-watch": "~0.4.4",
    "assemble-less": "~0.6.0",
    "grunt-contrib-copy": "~0.4.1",
    "grunt-contrib-cssmin": "0.6.1",
    "grunt-contrib-uglify": "~0.2.2",
    "grunt-contrib-clean": "~0.5.0",
    "grunt-contrib-requirejs": "~0.4.1",
    "grunt-text-replace": "~0.3.6",
    "grunt-fileindex": "~0.1.0",
    "grunt-ssh": "~0.6.3",
    "grunt-concurrent": "~0.4.2",
    "time-grunt": "~0.2.5",
    "grunt-contrib-concat": "~0.3.0",
    "grunt-replace": "~0.7.6"
  },
  "engine": "node >= 0.10.0"
}

src1.less

.src1 {
  background-image: url('../src1/dummy.png');
}

src2.less

.src2 {
  background-image: url(../src2/dummy.png);
}