+ my $compare = (
+ !defined $ver ? undef : # last column if nameless
+ ref $data ne 'HASH' ? '' : # unclassified if no support hash
+ $data->{$ver} // $prev # known or inherit from predecessor
+ // (grep { defined } @{$data}{ @{ $versions{$browser} } })[0]
+ ~~ 'n' && 'n' # first known version is unsupported
+ || 'u' # unsure
+ );
+ unless (!defined $prev or $prev ~~ $compare) {