my $input = shift;
return undef unless defined $input;
- # no '.' or '..' as elements of path, i.e. no '.' nor '..'
+ # no '.' or '..' as elements of path, i.e. no '.' or '..'
# at the beginning, at the end, and between slashes.
# also this catches doubled slashes
if ($input =~ m!(^|/)(|\.|\.\.)(/|$)!) {