public/libs/less.js/1.3.1/less.js
function () {
                    var value, c = input.charCodeAt(i);
                    if ((c > 57 || c < 45) || c === 47) return;

                    if (value = $(/^(-?\d*\.?\d+)(px|%|em|pc|ex|in|deg|s|ms|pt|cm|mm|rad|grad|turn|dpi|dpcm|dppx|rem|vw|vh|vmin|vm|ch)?/)) {
                        return new(tree.Dimension)(value[1], value[2]);
                    }
                }
function () {
                    var value, c = input.charCodeAt(i);
                    if ((c > 57 || c < 45) || c === 47) return;

                    if (value = $(/^(-?\d*\.?\d+)(px|%|em|pc|ex|in|deg|s|ms|pt|cm|mm|rad|grad|turn|dpi|dpcm|dppx|rem|vw|vh|vmin|vm|ch)?/)) {
                        return new(tree.Dimension)(value[1], value[2]);
                    }
                }
function ( ) { var value , c = input . charCodeAt ( i ) ; if ( ( c > 57 || c < 45 ) || c === 47 ) return ; if ( value = $ ( / ^(-?\d*\.?\d+)(px|%|em|pc|ex|in|deg|s|ms|pt|cm|mm|rad|grad|turn|dpi|dpcm|dppx|rem|vw|vh|vmin|vm|ch)? / ) ) { return new ( tree . Dimension ) ( value [ 1 ] , value [ 2 ] ) ; } }
A Dimension, that is, a number and a unit  0.5em 95%
A Dimension that is a number and a unit 0 . 5em 95%