$comment{$lineno++} = $_;
##</code><code>##

push(@lines, { id => $id, line => $_ }); $lineno++;
##</code><code>##

@lines = sort { $a->{id} <=> $b->{id} } @lines;
for (0..$lineno-1) {
    if (exists $comment{$_}) { print $comment{$_}; }
    else { my $x = shift(@lines); print $x->{line}; }
}
# @lines should be empty at this point