my (@isec , @b ) = ();
(@b, @isec) = ArrayFunctions(\@ArrayA, \@ArrayB, \@b, \@isec);
sub ArrayFunctions
{
    my $a_ref = shift; # reference to input array A
    my @a = @$a_ref; # input array A
    my $b_ref = shift; # reference to input array B
    my @b = @$b_ref; # input array B
    my $b = shift; # input array Bonly
    my $isec = shift; # input array isec_plus_bonly

    my @Aseen{@a} = (); # lookup table
    my @Bseen{@b} = (); # lookup table
#.......... Other Code .....
}