Well, it's only special in that it's silently twiddled into while( defined( $_ = <filehandle> ) ) { ... }; it otherwise is still looping until the value of the expression is false (the twiddling being done so that lines that would otherwise be interpreted a boolean false (e.g. 0\n) are differentiated from the diamond-operator-returns-undef-on-eof false value).</pedant>