What version of CGI do you have ?. In 3.65 the code was

sub STORE {
    my $self = shift;
    my $tag  = shift;
    my $vals = shift;
    my @vals = index($vals,"\0")!=-1 ? split("\0",$vals) : $vals;
    $self->param(-name=>$tag,-value=>\@vals);
}
[download]

In 4.37 it is

sub STORE {
    my $self = shift;
    my $tag  = shift;
    my $vals = shift;
    my @vals = defined($vals) && index($vals,"\0")!=-1 ? split("\0",$v
+als) : $vals;
    $self->param(-name=>$tag,-value=>\@vals);
}
[download]

Was 4.22. Have upgraded to 4.38. Thank you)))