# if @ds1_rows is an AofA holding a dataset, then...
for my $a ( @ds1_rows ) {
        
        # $record1 is an array, not a scalar... you are deref-ing 
        # an arrayref and assigning it to a scalar, which doesn't 
        # make any sense
	my $record1 = "@$a";
	my $bool = '';

# then, further on...
       # you are assigning each element to $aref 
       # (where is the 'my'?)...
       for $aref ( @ds2_rows )  {
                    # and then, not using $aref... 
                    # instead, you are using $a again
                    my $record2 = "@$a";

##</code><code>##

#Simple solution for union and intersection
foreach $e (@a) { $union{$e} = 1 }

foreach $e (@b) {
    if ( $union{$e} ) { $isect{$e} = 1 }
    $union{$e} = 1;
}
@union = keys %union;
@isect = keys %isect;