#! perl -sw
use strict;

# Without the next %table referes to a global var which doesn't declaration.
my %table;

while (<>) {
	chomp;
	my ($city, $country) = split /, /;
	push @{$table{$country}}, $city;
	# The line above is equivalent to 
=pod	
	if (not exists $title{$country}) {
		my @array;
		push @array, $city;
		$title{$country} = \@array;
	} else {
		my $arrayRef = $title{$country};
		push @{$arrayRef}, $city;
	}
=cut
}

foreach my $country (sort keys %table) {
	print "$country: ";
	my @cities = @{$table{$country}};
	print join ',', sort @cities;
	print ".\n";
	#The 3 lines above could be replaced by 
=pod
	print join( ',' @{$table{$country}} ), "\n";
=cut
}