If distance( Pirate.X, Pirate.Y, Player.X, Player.Y ) < 50
 If angle( Pirate.X, Pirate.Y, Player.X, Player.Y ) < 0
 If angle( Pirate.X, Pirate.Y, Player.X, Player.Y ) > 180
 Pirate rotate to the left

 If angle( Pirate.X, Pirate.Y, Player.X, Player.Y ) < 180
 If angle( Pirate.X, Pirate.Y, Player.X, Player.Y ) > 0
 Pirate rotate to the right
 = "if distance" event block.
You'll need to adjust the angle tests if you want it within a certain range.