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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