You've received excellent scripting suggestions. Still, perhaps the following minor modifications of your script will be helpful:

use strict;
use warnings;
use DateTime;
use POSIX qw(strftime);
use autodie;

open my $logFH, '<', 'second.txt';

while (<$logFH>) {
    my ( $streamname, $streamid, $timedate ) = split /[@\s]/;
    my $time_t = POSIX::strftime( "%Y-%m-%d %r", localtime($timedate) 
+);

    open my $fh, '>', "$streamid/$streamname";

    print $fh <<END;
<event>
  <stream-id>$streamid</stream-id>
  <event-name>$streamname</event-name>
    <primary-event>
    <delete-time>$time_t</delete-time>
    </primary-event>
</event>
END
}
[download]

• Always: use strict; use warnings;
• Used a single split
• Used the three-argument open()
• Used a here document for printing.
• A close is absent above, since the currently-opened file will automatically close when a new handle is assigned to $fh

Edit: Added use autodie; to catch any silent close failures. Thank you, davido.