http://www.perlmonks.org?node_id=511392


in reply to Sorting Dates

If you want to go with your original approach, the following maybe useful: 

my @dates = qw(5/7/2001 3/10/2005 1/1/1996 2/1/1993);

foreach my $date (@dates) {
  if ($date =~ m|(\d{1,2})/(\d{1,2})/(\d{4})|) {
    my $new_date = sprintf("%d/%02d/%02d", $3, $2, $1);
    ...
  }
}

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Hope this helps, -gjb-

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Re^2: Sorting Dates
by josephjohn (Acolyte) on Nov 24, 2005 at 10:51 UTC
    Thanks for the suggestion gjb. Does that sort the hash too. I need to sort the dates, find the last date, and perform some calculations later in the script. Also please let me know what qw() is used for.
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      This doesn't sort the hash, it only converts the date from D/M/YYYY to YYYY/MM/DD so that it can be used as a key in your %datecount hash. This hash can be sorted the way you do it in your code fragment.

      As to qw: 

      $ perldoc -f qw
    qw/STRING/
      Generalized quotes.  See "Regexp Quote-Like Operators"
      in perlop.

      [download]
      It returns a list of words without doing interpolation on them. It is just a convenient way of writing: 
        my @dates = ('5/7/2001' '3/10/2005' '1/1/1996' '2/1/1993');

      [download]

      Hope this helps, -gjb-

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      >Does that sort the hash too

      You cannot sort a hash : a hash is by construction with no particular order. What you can do is sort the keys of a hash and print the corresponding values.

      When you do  foreach (keys %hash) you get the keys in an order that is undefined although always the same. But it will change if you add or remove keys, therefore if you need a specific order you should do  foreach ( sort { my sort function} keys %hash )

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