lib/less/parser/parser.js
function (parsedName) {
                var lookups, important, i = parserInput.i,
                    inValue = !!parsedName, name = parsedName;

                parserInput.save();

                if (name || (parserInput.currentChar() === '@'
                    && (name = parserInput.$re(/^(@[\w-]+)(\(\s*\))?/)))) {

                    lookups = this.mixin.ruleLookups();

                    if (!lookups && ((inValue && parserInput.$str('()') !== '()') || (name[2] !== '()'))) {
                        parserInput.restore('Missing \'[...]\' lookup in variable call');
                        return;
                    }

                    if (!inValue) {
                        name = name[1];
                    }

                    if (lookups && parsers.important()) {
                        important = true;
                    }

                    var call = new tree.VariableCall(name, i, fileInfo);
                    if (!inValue && parsers.end()) {
                        parserInput.forget();
                        return call;
                    }
                    else {
                        parserInput.forget();
                        return new tree.NamespaceValue(call, lookups, important, i, fileInfo);
                    }
                }

                parserInput.restore();
            }
function (parsedName) {
                var lookups, important, i = parserInput.i,
                    inValue = !!parsedName, name = parsedName;

                parserInput.save();

                if (name || (parserInput.currentChar() === '@'
                    && (name = parserInput.$re(/^(@[\w-]+)(\(\s*\))?/)))) {

                    lookups = this.mixin.ruleLookups();

                    if (!lookups && ((inValue && parserInput.$str('()') !== '()') || (name[2] !== '()'))) {
                        parserInput.restore('Missing \'[...]\' lookup in variable call');
                        return;
                    }

                    if (!inValue) {
                        name = name[1];
                    }

                    if (lookups && parsers.important()) {
                        important = true;
                    }

                    var call = new tree.VariableCall(name, i, fileInfo);
                    if (!inValue && parsers.end()) {
                        parserInput.forget();
                        return call;
                    }
                    else {
                        parserInput.forget();
                        return new tree.NamespaceValue(call, lookups, important, i, fileInfo);
                    }
                }

                parserInput.restore();
            }
Call a variable value to retrieve a detached ruleset or a value from a detached ruleset's rules.  @fink(); @fink; color: @fink[@color];