if (x == y) {
  trace("x and y are equal");
}

For the sake of terseness, ActionScript does not require curly braces when a conditional has only one substatement. A single substatement may quite legitimately be placed directly after an if or an else if statement without any curly braces, like this:

if (x == y) trace ("x and y are equal");

Or like this:

if (x == y)
  trace ("x and y are equal");

For some programmers, this style can be a little slower to read and slightly more error prone, though it undeniably saves room in source code.

7.4. Simulating the switch Statement		7.6. Onward!