#!/usr/bin/perl
use Modern::Perl;

say "\n\n\t sort on multiple keys";

my @first = qw(John Joe John Jon Fred Rich);
my @last = qw(Smith Smith Jones Jackson Jones Adler);

my @index = sort {
	$last[$a] cmp $last[$b]
	or
	$first[$a] cmp $last[$b]
} 0 .. $#first;

for (@index) {
	say "$last[$_], $first[$_]";
}

say "\n \t But, testing, single sort (cmp):";


my @sorted = sort { $a cmp $b  } qw(John Joe John Jon Fred Rich);
for (@sorted) {
	say "\t $_";
}


=head execution

         sort on multiple keys
Adler, Rich
Jackson, Jon
Jones, John
Jones, Fred
Smith, John
Smith, Joe

         But, testing, single sort (cmp):
         Fred
         Joe
         John
         John
         Jon
         Rich

## sort puts "John" before "Joe" in the first instance but not in the second: Why?

=cut