I'd rather write to a temporary file and rename it at the end

Good thing I wrote a module for that ;-)

use warnings;
use strict;
use File::Replace 'replace2';

my ($infh,$outfh) = replace2(__FILE__);
while (<$infh>) {
    last if /^__DATA__$/;
    print $outfh $_;
}
print $outfh "__DATA__\n";
print $outfh "New stuff! ".gmtime." UTC\n";
close $infh;
close $outfh;
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Still using the tell of the DATA filehandle is the far better approach.

There is no guaranty to correctly match __DATA__ without having a full Perl parser.

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Wikisyntax for the Monastery}

Still using the tell of the DATA filehandle is the far better approach.

You are correct, and thank you for the inspiration :-) I just released v0.08 of File::Replace with a new copy method:

use warnings;
use strict;
use File::Replace 0.08 'replace3';

my ($infh,$outfh,$repl) = replace3(__FILE__,':raw');
$repl->copy(tell(DATA));
print $outfh "New stuff! ".gmtime." UTC\n";
$repl->finish;

__DATA__
[download]

Or use a locking mechanism (e.g. flock).