-ㄹ라고 is a relaxed, regionally coloured way of saying -려고 'intending to': 그냥 넘어갈라고 했는데 'I was just going to let it slide.' It gives the reason behind an action and here usually leads into a second clause such as 했는데 or 하고 있는데. It sounds folksy and unbuttoned; in writing you would use -려고.