{
    my( $indent, $depth ) = ( "\t", 0 );
    sub pp {
        my $next_depth;
        my( $end_chunk, $first ) = f1( $str );
        if( defined $first ) {
            if( $first eq CONST1 ) {
                ++$end_chunk;
                $next_depth = --$depth;
            }
            elsif( defined my $pos2 = f2( $str, $first ) ) {
                $next_depth = $depth;
                $end_chunk = $pos2 + 2;
            }
            else {
                $next_depth = $depth + 1;
            }
        }
        else {
            $next_depth = $depth;
        }

        print $indent x $depth, substr( $str, 0, $end_chunk );
        $str =~ s[^.{$end_chunk}\s*][];
        $depth = $new_depth;
        return;
    }
}