Abhisek has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Unique number
by stiller (Friar) on Feb 13, 2008 at 06:38 UTC 
    my %seen = ();
my @uniq = ();
foreach $item (@proc_name1) 
{
   unless (exists $seen{$item}) # if $item not already in %seen 
   {
       $seen{$item} = 1;     # every item seen
       push (@uniq, $item);  # and again
   }
}

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    It is better to test for existence when you want to know if some key is already in a hash. It's faster and it avoids the automatic creation of an entry (autovivification).
    Also, the use of unless is often rather hard to comprehend, the meaning of
    if (! exists $seen{$item})
    is clearer.

    The two lines adding $item to %seen and @uniq both do the same thing, keeping one record of each item seen.

    Does that answer your question?

    you could do this with a lot less code:

    my %seen;
$seen{$_} = 1 for (@proc_name1);

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      $seen{$_} = 1 for (@proc_name1);

      You don't actually need the parentheses around @proc_name1. You can also avoid the for loop if you wish by using a hash slice.

      my %seen;
@seen{@proc_name1} = ();

      [download]

      I hope this is of interest.

      Cheers,

      JohnGG

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