when (["svn", "svn-checkout", "path", "build", "git", "hg", "sysbuild", "bzr", "bzr-checkout"]) {

                when (["path", "build", "git", "hg", "sysbuild"]) {

                when (["svn", "svn-checkout", "bzr", "bzr-checkout"]) {
                    push @res, "--arg", $input, (
                        "{ outPath = builtins.storePath " . $alt->{storePath} . "" .
                        (defined $alt->{revision} ? "; rev = " . $alt->{revision} . "" : "") .
                        ";}"
                    );
                }