perl引用的實例

$ cat country
Chicago, USA
Frankfurt, Germany
Berlin, Germany
Washington, USA
Helsinki, Finland
New York, USA

 

#!/usr/bin/perl -w
use strict;
my %table;
my ($city,$country);
while (<>) {
 chomp;
 my ($city,$country) = split /,/;
 push @{$table{$country}},$city;
}

foreach $country (sort keys %table){
 print "$country:";
 my @cities = @{$table{$country}};
 print join ',', sort @cities;
 print ".\n";

}

result：

$ perl country.pl country
 Finland:Helsinki.
 Germany:Berlin,Frankfurt.
 USA:Chicago,New York,Washington.