Operator Precedence

It's that time again when I mention something that's already in the perldocs; this one is about operator precedence. Anyway today I found out that something like

my @a = qw(1);
print 'Yippeee!' if ( ! scalar(@a) >= 2 );

What does this print out? Yippeee!? Nope. The problem here is operator precedence. You may read it as the count of @a being greater than or equal to 2 and negate this (after all that's what ! normally means). Well what actually gets evaluated is ! count and then if this result is >= 2. Possible solutions to this are

print 'Yippeee!' if ( ! (scalar(@a) >= 2) );
print 'Yippeee!' if ( scalar(@a) < 2);

So the first deals with it by adding () to make sure the evaluation order is respected, the second replaces it for a more logical test.

What is the take home message? Everything in Perl has a precedence order.