You cannot unflatten two arrays from the parameter array. If you want to pass two arrays to a subroutine, use a reference:

arrayComp(\@a, \@b);
sub arrayComp {
    my ($aref, $bref) = @_;
    my @a = @$aref;
    my @b = @$bref;
[download]

Moreover, what do you think using (@a, @b) in the parameter list does?