Handlebars Eval Helper

eval.js

/**
 * Evalutes a given expression by taking in a hash of variables as input values.
 * ${variable} denotes a variable assigned in the hash.
 * 
 * Example:
 * 		{{eval "${a} + ${b}" a=1 b=2}}
 * 			= 3
 */
module.exports.register = function(Handlebars, options) {
	Handlebars.registerHelper('eval', function(expr, options) {
		var reg = new RegExp("\\${(\\S+)}", "g");
		var compiled = expr.replace(reg, function(match, pull){
			return options.hash[pull];
		});
		var evaluated = eval(compiled);

		return evaluated;
	});
}

Some example
http://jsfiddle.net/ppbntl19/kx1j68vz/2/