One common mistake that is made when assigning to a collection of scalars is this:

my ($one, $two, $three, $four) = 0;
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People tend to think that all four variables are initialized, but really only $one is set to zero, the rest are still undef. You'd have to explicitly set each variable to achieve that result:

my $one = my $two = my $three = my $four = 0;
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... or alternatively:

my ($one, $two, $three, $four) = (0,0,0,0);
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But as was stated elsewhere, this lacks readability for large collections of scalars. In general, I tend to declare my variables and either initialize them to zero or leave them undefined, then assigning their values in later statements. I hate getting warnings about variables being undef when evaluating in a conditional statement.