There's never any GOOD reason to go leaving parens out. Not on maintained code, anyway.
See the story on nuclear missiles and Perl.. with the mistake being blamed on an ASSUMED precedence order on an operation.
Even in this example use of parenthesis would have given this user the compile time warning he was looking for. Even smarter would be to add argument expections to the prototype:
sub chk_timer( $ );
But programmers like to think they are smarter than that and take risks. So do a lot of American drivers refusing to wear their seatbelts. That's ok, an ego is a precious thing, except in professional circles. If you can't program to protect against yourself, or drive wearing a seatbelt JUST IN CASE, then you have no defence when you look silly (or dead) at the end of the day.
The art of programming is like self defence, mastery of self. I am not perfect.. are you?