There is a much better answer in this case than storing multiple bits of information in the hash keys. I would personally never do that unless I absolutely had to. The example given in this question is actually a really simple data structure: One name to Multiple values, or in perl, a hash whose values are array references. Enough lecturing now.

my %countries = ();
my $foo = "US:New York";
my ($country, $city) = (split /:/, $foo);
push @{ $countries{$country} }, $city;
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This code assumes you understand references in perl.

Then to print all the cities within the country:

foreach my $city (@{$countries{$country}}) {
    print "$city\n";
}
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It's trivial to include even more information than that as well; turn that array reference into a hash reference by city, containing maybe another hash reference with even more information or an array with a list of people who live there.

my %data = (
    'US' => {
        Florida => 'Miami',
        Illinois => 'Chicago',
        New York => 'New York City' },
    'Canada' => {
        British Columbia => 'Alberta',
        Saskatchewan => 'Saskatoon',
        Ontario => 'Toronto' }
);
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(Oh, a hash is an associative array. That means that it takes the first element -- New York, for example -- and runs it through a hashing algorithm to generate a unique index, which helps it locate the key -- New York City -- in an internal data structure. If the hashing algorithm is good, "New York" will always come up with the same hash value, which is why duplicate keys are not very useful.)

@cities = qw/ US:Miami AU:Melbourne US:Chicago /;

map {my($co,$ci)=split/:/,$_; $n{$co}{$ci}=1 } @cities;

foreach $x (sort keys %n) {
   foreach (sort keys %{$n{$x}}) {
        printf "$x - $_\n";
   }
}
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open(MYFILE, "$cityfile") || die "Could not open $cityfile: $!\n";
while(<MYFILE>) {
  chomp;
  ($city, $country) = split(/:/, $_);
  $place{$country} .= "$city#";
}
close(MYFILE); 
for $x (keys %place) {
  print "$x:\n";
  for (split(/#/, $place{$x})) {
    print "\t$_\n";
  }
}
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map {my $key=$_;map {print "$key - $_\n"}
sort keys %{$n{$_}} } sort keys %n;
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open (FILE,"c:/file.txt");
%hash=();
while (<FILE>)
      {chomp;
      split /:/;
      if ($hash{$_[0]}){$hash{$_[0]}.=",$_[1]";}
      else {$hash{$_[0]}=$_[1];}
      }
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HI, I'm not able to execute the script u have written. I have a requirement like this: original file: 38881,408 38884,596 38884,597 38884,607 38884,608 38884,609 38884,615 output expected: 38881:408 38884:596,597,607,608,609,615 Could you plz. help me to get this output done

Re: Can a hash name have the same value twice.

Originally posted as a Categorized Answer.

Originally posted as a Categorized Answer.