my $string = 'foo bar baz';

$string =~ /(\w+) (\w+) (\w+)/;

print "1: $1, 2: $2, 3: $3\n";

$string =~ /(\w+) (?:\w+) (\w+)/;

print "1: $1, 2: $2\n";

print "3: is empty\n" unless $3;