# you originally have two parallel arrays of related data
my @a = (6, 7, 8);
my @b = (3, 2, 1);

# So you need to use artificial means to put the data together, such as an index variable
for my $index (0 .. $#a) {
   my ($a,$b) = ($a[$index], $b[$index]);
   print $a, "\n" if $b>1;
}

# If instead you keep the related data items together in a two-dimensional array:
my @c = (  [6,3], [7,2], [8,1] );

# Then printing the related data is easy, and you needn't track the array index
for my $item (@c) {
   my ($a,$b) = @$item;
   print $a, "\n" if $b>1;
}