So, I think this problem is hard because the statements are obvious, and don't seem to need proof!
In a two column proof, I would use two statements other than given.
Given: lines l and m are perpendicular. Prove: Lines l and m form a 90 degree angle.
1. Lines l and m are perpendicular 1. Given
2. Lines l and m form a right angle 2. Definition of perpendicular
3. Lines l and m form a 90o angle 3. Definition of a right angle
To prove the converse, just work backwards: if two lines form a 90 degree angle, then they form a right angle, by definition of a right angle. Since the lines form a right angle, they are perpendicular, by the definition of perpendicular.
(Note: Hopefully your book definition of perpendicular says "two lines are perpendicular if they meet at a right angle" because the definition of "perpendicular" can vary a bit from text to text!)