Tou forgot to unset your flag 
#!/usr/bin/perl

use strict;
use warnings;
my $flag=0;
while(<DATA>){
        if (/\{AUTHOR\}/){
                $flag=1;
                next;
        }
        if (/^\{/){
                $flag=0;
                next;
        }
        print $_ if $flag;
}


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

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In reply to Re^5: regular expression by Utilitarian
in thread regular expression by Anonymous Monk

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