sub blank_formatter {
  my ($printf_format, $length) = @_;
  if (!defined($length))
  {
    $printf_format =~ /^%(\d+)/ or die "Can't deduce length from $printf_format";
    $length = $1;
  }
  my ($blank) = ' ' x $length;
  sub { $_[0] ? sprintf($printf_format,$_[0]) : $blank; };
}

sub my_printf
{
  my ($format, @args) = @_;
  my (@printfargs) = ();
  while (@args) {
    my $arg = shift @args;
    if (ref($arg) and ref($arg) eq 'CODE') {push @printfargs, $arg->(shift @args);}
    else {push @printfargs, $arg;}
  }
  printf($format, @printfargs);
}
# similarly, if you need it, my_sprintf

# Was:
# printf( "A float: %12.4f$/", $root_beer );
my_printf( "A float: %s$/", blank_formatter('%12.4f'), $root_beer );