This one is indead IlyaM proof :) I stared on it for 5 mins and I could not find how it can be abused ++. Anyway I'm not sure I like this approach because it is very easy to do mistakes. I would not use regexps on whole string but I'd split path on components first and then I'd use regexps on them. I.e. something like:

use URI;
my $uri = URI->new($path);
die "bad schema" unless is_safe_schema($uri->schema);
die "bad domain" unless is_safe_domain($uri->host);
die "bad path" unless is_safe_path($uri->path);

sub is_safe_schema {
    # left as excersize to reader
}

sub is_safe_domain {
    # left as excersize to reader
}

sub is_safe_path {
    my $path = shift;
    my @comps = split '/', $path;
    for my $comp (@comps) {
        return 0 unless is_safe_path_comp
    }
    return 1;
}

sub is_safe_path_comp {
    my $comp = shift;
    return 0 if $comp =~ /\0\\/;
    return 0 if $comp eq '..';
    # other unsafe patterns
    ....
    return 1;
}
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--
Ilya Martynov, ilya@iponweb.net
CTO IPonWEB (UK) Ltd
Quality Perl Programming and Unix Support UK managed @ offshore prices - http://www.iponweb.net
Personal website - http://martynov.org

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