Returns the path shortened and handles paths with //'s together like ////usr/bin correctly. Returns undef in the special case of the root path. Does not handle relative paths

sub pathtrim
{
    my($path)=@_;
    return undef if($path eq '/');
    $path =~ s#/[^/]+$#/#;
    $path =~ s#(/[^/]*)/+$#$1#;
    return $path;
}
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