$-[0] is the offset of the start of the last successful 
match. $-[n] is the offset of the start of the substring 
matched by n-th subpattern, or undef if the subpattern 
did not match. 


for (qw(foo bar baz)) {
	if (/(foo)|(bar)|(baz)/) {
		print "\$+ = $+\n";
		print "\@- = " . join('/',@-) . "\n";
		print "scalar \@- = " . scalar(@-) . "\n";
	}
}
__END__

$+ = foo
@- = 0/0
scalar @- = 2
$+ = bar
@- = 0//0
scalar @- = 3
$+ = baz
@- = 0///0
scalar @- = 4