$c1 = substr $s1, $i, 1;
my $c2 = length $s2 <= $i ? undef : substr $s2, $i, 1;
my $next = $i + 1 >= length($s1) ? $c1 : chr( ord($c1) + 1 );
- $next le $c2 or next if defined $c2;
my $last = defined $c2 && $i == 0 ? chr( ord($c2) - (length $s2 > 1) ) : 'z';
+ $next le $last or next if defined $c2;
push @allow, $prefix."[$next-$last]";
}
continue {