my %hash2 =(
           '1' => 2,
           '3' => 5,
           '4' => 2,); 

##</code><code>##

$VAR1  = 
{
          '3-3' => 5,
          '3-4' => 10,
          '1-1' => 2,
          '3-1' => 10,
          '1-4' => 4,
          '4-4' => 2,#ends here
};

##</code><code>##

use strict;
use warnings;
use Data::Dumper;

#print Dumper \%hash2;
my %spair = ();
my $prod;
foreach my $si (keys %hash2)
  {
    foreach my $sn (keys %hash2)
      {    
           if ($si == $sn)
	     {
               $prod = $hash2{$si};
	     }
           else
	     { $prod = $hash2{$si}*$hash2{$sn};
	     }
           $spair{$si."-".$sn} = $prod;  
      }
  }
print Dumper \%spair;

##</code><code>##

$VAR1 = {
          '3-3' => 5,
          '3-4' => 10,
          '1-1' => 2,
          '3-1' => 10,
          '1-4' => 4,
          '4-4' => 2,
          '4-1' => 4, #repeat
          '1-3' => 10,#repeat
          '4-3' => 10 #repeat
        };