my $fmt;      # prototypes are documentary (rt#89053)
      my $given = [ sub ($$) { $_[0] =~ /^[-+]?[0-9]+\.?\z/     && q{%s}  },
                    sub ($$) { $_[1]                            && qq{%s}},
                    sub ($$) { 1 == length($_[0])               && q{'%s'}},
                    sub ($$) { $_[0] =~ m{^(?:[+-]?(?:\.[0-9]+)
                              | (?:[0-9]+\.[0-9]+))\z}x         &&  q{%.2f}},
                    sub ($$) { substr($_[0],0,5) eq 'HASH('     && 
                                                '{'.sw(ellipsis).'}'  },
                    sub ($$) { substr($_[0],0,6) eq 'ARRAY('    && 
                                                '['.sw(ellipsis).']'  },
                    # sub ($$) { $mxstr && length ($_[0])>$mxstr 
                    #           && qq("%.${mxstr}s")},
                    sub ($$) { 1                                && q{"%s"}} ];

      do { $fmt = $_->($v, $ro) and last } for @$given;
      return sprintf $fmt, $v;