gistfile1.txt

my @spans = lines q:to/SPANS/;
      <----->
         <----------->
               <---->
               <----->
                  <------------------->
                        <---->
                        <----->
                           <-------->
                                 <---->
<----->
   <-------->
         <---->
SPANS


constant $max = 40;
my @available = @spans».trim.sort: -*.chars;

say "=" x $max;

put join "", gather loop {
    my $cur = 0;
    for ^@available -> $i {
        last if $i >= @available;
        if @available[$i].chars + $cur <= $max {
            $cur += @available[$i].chars;
            @available.splice($i,1).take;
            redo;
        }
    }
    last unless @available;
    $cur = 0;
    take "\n";
}