+my @browsers = keys %versions;
+
+print <<'';
+<p id="intro">Alternate rendition of Fyrd's <a href="http://caniuse.com/">when can I use...</a> page
+
+my ($canihas, $usage);
+given ($get{usage} // 'wm') {
+ when (!$_) {
+ # none
+ }
+ when (!/^[a-z][\w-]+$/) {
+ printf "<p>Invalid browser usage data request: <em>%s</em>",
+ 'identifier must be alphanumeric name or <q>0</q>';
+ }
+ $canihas = do "browser-usage-$_.inc.pl" or do {
+ printf "<p>Browser usage data not found: <em>%s</em>", $! || $@;
+ break;
+ };
+ $usage = $_;
+ my $ref = $canihas->{-title} || 'unknown';
+ $ref = sprintf '<a href="%s">%s</a>', $_, $ref
+ for $canihas->{-site} || $canihas->{-source} || ();
+ $ref .= " $_" for $canihas->{-date} || ();
+ print "\nwith $ref browser usage statistics";
+}
+if ($usage) { # first() does not work inside given >:(
+ # adapt version usage to actual support data
+ my %engineuse; # prefix => usage sum
+ while (my ($browser, $row) = each %$canihas) {
+ my $verlist = $versions{$browser} or next;
+ my %supported = map { $_ => 1 } @$verlist;
+
+ # cascade unknown versions
+ $row->{$_} //= undef for @$verlist; # ensure stable keys during iteration
+ while (my ($version, $usage) = each %$row) {
+ next if defined $supported{$version};
+ my $next = first { paddedver($_) ge paddedver($version) } @$verlist
+ or warn("No fallback found for $browser v$version; $usage% ignored"), next;
+ $row->{$next} += $usage;
+ $row->{$version} = 0; # balance browser total
+ }