source: node_modules/prismjs/components/prism-less.js

/* FIXME :
 :extend() is not handled specifically : its highlighting is buggy.
 Mixin usage must be inside a ruleset to be highlighted.
 At-rules (e.g. import) containing interpolations are buggy.
 Detached rulesets are highlighted as at-rules.
 A comment before a mixin usage prevents the latter to be properly highlighted.
 */

Prism.languages.less = Prism.languages.extend('css', {
        'comment': [
                /\/\*[\s\S]*?\*\//,
                {
                        pattern: /(^|[^\\])\/\/.*/,
                        lookbehind: true
                }
        ],
        'atrule': {
                pattern: /@[\w-](?:\((?:[^(){}]|\([^(){}]*\))*\)|[^(){};\s]|\s+(?!\s))*?(?=\s*\{)/,
                inside: {
                        'punctuation': /[:()]/
                }
        },
        // selectors and mixins are considered the same
        'selector': {
                pattern: /(?:@\{[\w-]+\}|[^{};\s@])(?:@\{[\w-]+\}|\((?:[^(){}]|\([^(){}]*\))*\)|[^(){};@\s]|\s+(?!\s))*?(?=\s*\{)/,
                inside: {
                        // mixin parameters
                        'variable': /@+[\w-]+/
                }
        },

        'property': /(?:@\{[\w-]+\}|[\w-])+(?:\+_?)?(?=\s*:)/,
        'operator': /[+\-*\/]/
});

Prism.languages.insertBefore('less', 'property', {
        'variable': [
                // Variable declaration (the colon must be consumed!)
                {
                        pattern: /@[\w-]+\s*:/,
                        inside: {
                                'punctuation': /:/
                        }
                },

                // Variable usage
                /@@?[\w-]+/
        ],
        'mixin-usage': {
                pattern: /([{;]\s*)[.#](?!\d)[\w-].*?(?=[(;])/,
                lookbehind: true,
                alias: 'function'
        }
});