use warnings;
use strict;

while (<DATA>) {
    print if s/{AUTHOR}\n// .. (s/{AUTHOR}\n//, s/{(?!AUTHOR})\w+}\n//);
}

__DATA__
{TAG}
tag1
{AUTHOR}
By June Fletcher
JOURNAL
{TAG}
tag2
TOM MacCUBBIN
{DATA}
data1
{AUTHOR}
Richard White
{AUTHOR}
MacCUBBIN
{SOUR}

##</code><code>##

By June Fletcher
JOURNAL
Richard White
MacCUBBIN