my %Accountinfo;

$Accountinfo{E200} = [200, 300, 400];
$Accountinfo{E400} = ["EFG"];

#Now , you can iterate through all stores for all accounts:

for my $acct (sort keys %Accountinfo){

   for my $store (@{ $Accountinfo{$acct} } ){
      print "Account $acct has store $store\n";
   }

}