[Perl-beginners] Syntax for if

On 2/8/10, Chris Coggins wrote:
What is the proper syntax for a comparison at the end of a subroutine to
stop the script if a certain variable is "0" or ''?

sub routine{
(get data and process it)
if $varA = '' || $varA = "0" {
(stop script, print error message to user)
}
else{
(continue with script)
}