This if ($hash{foo} = 42) is an assignment statement and the if tests the result of that.
 if ($hash{foo} == 42) would probably do something else.

for all my goofs above, I don't see how a properly formatted, syntactically correct "if" statement, a question in essence, can cause a new element to be entered into a data structure. I can see how this above statement could do that, but that is because it is more than a simple logical "if".