1 #!/usr/bin/perl
2 
3 # Get the rightmost program running (you can get the program from the
4 # Downloads section of http://www.intermediateperl.com/ if you don't want to
5 # type the whole thing yourself). Once you have the example working, modify
6 # the rightmost program, take a hash reference of patterns, and return the
7 # key of the rightmost match. Instead of calling it like:
8 #
9 # my $position = rightmost(
10 #	'There is Mrs. Howell, Ginger, and Gilligan',
11 #	@patterns{ sort keys %patterns }
12 # );
13 #
14 # call it like:
15 #
16 # my $key = rightmost(
17 #	'There is Mrs. Howell, Ginger, and Gilligan',
18 #	\%patterns
19 # )
20 
21 use v5.24;
22 use warnings;
23 use strict;
24 use utf8;
25 
26 sub rightmost {
27 	my( $string, $pattern_ref ) = @_;
28 
29 	my $rightmost = -1;
30 	my $rightkey;
31 	while ( my ($key, $regex) = each %$pattern_ref) {
32 		my $position = $string =~ m/$regex/ ? $-[0] : -1;
33 			if ($position > $rightmost) {
34 				$rightmost = $position;
35 				$rightkey = $key;
36 			}
37 	}
38 	return $rightkey;
39 }
40 
41 my %patterns = (
42 	Gilligan   => qr/(?:Willie )?Gilligan/,
43 	'Mary Ann' => qr/Mary Ann/,
44 	Ginger     => qr/Ginger/,
45 	Professor  => qr/(?:The )?Professor/,
46 	Skipper    => qr/Skipper/,
47 	'A Howell' => qr/Mrs?. Howell/,
48 
49 );
50 
51 my $key = rightmost(
52       'There is Mrs. Howell, Ginger, and Gilligan',
53       \%patterns
54 );
55 print "$key\n";