my $glob_class    = '*?\\[\\],{}:!^~';
 
sub quote {
    shift;
    my $quoted = join '',
        map { ( m|\A'\z|                  ? "\\'"    :
                m|\A'|                    ? "\"$_\"" :
                m|\A[$noquote_class]+\z|o ? $_       :
                                          "'$_'"   )
          } split /('+)/, $_[0];
    length $quoted ? $quoted : "''";
}