This is a newbie question, but what is the special variable, @-? For example, this code:

sub rightmost{
my($string, @patterns) = @_;

my $rightmost = -1;
while( my($i, $pattern ) each @patterns ) {
   $position = $string =~ m/$pattern/ ? $-[0] : -1;
   $rightmost = $position if $position > $rightmost;
}
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