sub remove {
    my $string = shift;
    $string =~ s/[^a-zA-Z0-9.\-_]//g;
    return $string;
}
sub replace {
    my $string = shift;
    $string =~ s/[^a-zA-Z0-9.\-_]/_/g;
    return $string;
}
sub reversable {
    my $string = shift;
    $string =~ s/([^a-zA-Z0-9.\-_])/sprintf('=%x',unpack('C',$1))/eg;
    return $string;
}