>perl -wMstrict -le
"my %ha = qw(ka1 va1 ka2 va2 ka3 va3);
 my %hb = qw(bk1 bv1 bk2 bv2 bk3 bv3);
 while (my ($ka, $va) = each %ha  and
        my ($kb, $vb) = each %hb
       ) {
   print qq{a: $ka => $va   b: $kb => $vb}
   }
"
a: ka1 => va1   b: bk3 => bv3
a: ka3 => va3   b: bk2 => bv2
a: ka2 => va2   b: bk1 => bv1