+sub rangematch {
+ my ($link) = @_;
+ my ($s1, $s2) = $link =~ /([^-]*) - ([^-]*)/x
+ or return qr/^\Q$link/i;
+ my @allow;
+
+ if (length $s1) {
+ my $prefix = '';
+ my $char;
+ for my $i (0 .. length($s1) - 1) {
+ $char = substr $s1, $i, 1;
+ my $next = $char;
+ $next = chr( ord($char) + 1 ) if length $s1 > $i + 1;
+ my $last = 'z';
+ if (length $s2 > $i) {
+ if ($s2 =~ /^\Q$prefix/) {
+ $last = substr $s2, $i, 1;
+ next if $char eq $last;
+ $last = chr( ord($last) - (length $s2 > 1) );
+ next if $next gt $last;
+ }
+ }
+ push @allow, $prefix."[$next-$last]";
+ }
+ continue {
+ $prefix .= $char;
+ }
+ }
+
+ if (length $s2) {
+ my $prefix = '';
+ my $char;
+ for my $i (0 .. length($s2) - 1) {
+ $char = substr $s2, $i, 1;
+ my $last = 'z';
+ if (length $s1 > $i) {
+ my $c1 = substr $s1, $i, 1;
+ if ($s1 =~ /^\Q$prefix/) {
+ next if $c1 eq $char;
+ }
+ }
+ push @allow, $prefix."(?![$char-$last])"
+ if $i or $s1 eq '';
+ }
+ continue {
+ $prefix .= $char;
+ }
+
+ push @allow, $prefix
+ if $s2 =~ /^\Q$prefix/ and $s1 le $s2
+ and not (length $s2 == 1 && length $s1 >= length $s2 && $s1 ne $s2);
+ }
+
+ my $match = sprintf @allow <= 1 ? '%s' : '(?:%s)', join('|', @allow);
+ return qr/^$match/i;
+}
+