Thank you so much guys for your kind help, I used the solution given by ikegami and it worked very well(and fast) for me. I found my answer and I am closing this thread. Thanks alot once again to all of you. 
my @unique_pssns = grep { not exists $assns{$_} } @pssns;

   print("The following PSSNs have no corresponding ASSNs:\n");
   print("$_\n") foreach @unique_pssns;

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In reply to Re^2: How to compare two associative arrays efficiently by viveks_19
in thread How to compare two associative arrays efficiently by viveks_19

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