my ($foo_a) = @_;                       # Simple
my $foo_a = shift;                      # Comparable
my ($foo_a) = (shift);                  # Odd

my ($foo_a, $foo_b) = @_;               # Typical
my ($foo_a, $foo_b) = (shift, shift);   # Odder

my ($foo_a, $foo_b, $foo_c, $foo_d) = @_;
my ($foo_a, $foo_b, $foo_c, $foo_d) = (shift, shift, shift, shift);