use Data::Dump qw/pp/;
#...
    if ( -s $file and ! $do_rebuild ) {
        warn "reading cache";
        $h_func_pod = do $file;
        #warn pp '$h_func_pod: ', $h_func_pod;
    } else {                            # rebuild cache
        $h_func_pod = parse_by_process();
        warn "dumping to cache";
        open my $cache, '>', $file;
        print $cache ( '+' . pp $h_func_pod); # +{ is never a block
        close $cache;
    }