explanation of sentence

Hi, I vas translating the following : <!ENTITY return.falseproblem '<warning><simpara>This function may return &false;, but may also return a value evaluating to &false; in a simple if statement. Please use <link linkend="language.operators.comparison">the === operator</link> for testing the return value of this function.</simpara></warning>'> found in 'language-snippets.ent', but i cant get the meaning of this sentence: "but may also return a value evaluating to &false; in a simple if statement". Could please anybody help me? Thanks, Simone. -- "Eternal vigilance is the price of liberty" - Wendell Phillips