code: function(string, variables, shouldWrap) {
  			var instance = this;
  
  			return string.replace(INTERPOLATION_MATCHER, function(variable, variableName) {
  				var value;
  
  				// Either return the variable value or the original expression if it doesn't exist
  				if (variables[variableName] !== undefined) {
  					value = variables[variableName];
  				} else if (process.env[variableName] !== undefined) {
  					value = process.env[variableName];
  				}
  
  				if (value !== undefined) {
  					if (shouldWrap) {
  						// Escape all double quotes and wrap the value in double quotes
  						return instance._wrap(variables[variableName]);
  					}
  
  					return value;
  				}
  
  				return variable;
  			});
  		}
docs: /* Private Methods