A possible way... 
#!/usr/bin/perl

use strict;

my @files = do { local $/ = '^C^D^V^V^A'; <DATA> };

for (@files) {
    my %tags = ();
    my (@temp_keys) = $_ =~ /\{(\w+)\}/g;
    map { $tags{$_}++ } @temp_keys;

    for ( keys %tags ) {
        if ( $tags{$_} > 1 ) {
            print "The key $_ is multiple.\n";
        }
        else {
            print "$_\n";
        }
    }
}

__DATA__
^C^D^V^V^A os01 0002 010101 R S 0012310002 00003466^B{IT}
R
{SOURCETAG}
0012310002
{ACCESSION}
000000
{PUBLICATION}
THE ORLANDO SENTINEL
{EDITION}
METRO
{DATE}
010101
{DATE}
010102
{TDATE}
Monday, January 1, 2001
{SECTION}
SPECIAL SECTION
{PAGE}
E2
{ZONE}
FLORIDA
{KEYWORDS}
VOLUNTEER SUPPORT
{SECTION}
SPECIAL SECTION1
{SEND}
YES
^C^D^V^V^A os01 0003 010101 R S 0012310003 00001558^B{IT}
R
{SOURCETAG}
0012310003
{ACCESSION}
000000
{PUBLICATION}
THE ORLANDO SENTINEL
{HI}hi
{EDITION}
METRO
{DATE}
010101
{TDATE}
Monday, January 1, 2001
{SEND}
YES

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In reply to Re: remove duplicate tags by bichonfrise74
in thread remove duplicate tags by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
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