Something like this? 

#! perl -slw
use strict;

my $data = do{ local $/; <DATA> };

1 while $data =~ m[
    DOCUMENTS \n\n  ( .*? )     \n\n(?= AUTHOR: )
        (?{ print "<title> $^N </title>"     })
    AUTHOR:         ( .*? )     \n\n(?= SUBJECT: )
        (?{ print "<author> $^N </author>"   })
    SUBJECT:        ( .*? )     \n\n(?= BODY: )
        (?{ print "<subject> $^N </subject>" })
    BODY:           ( .*? ) (?: \n\n(?=\d+ \s of ) | $ )
        (?{ print "<body> $^N </body>"       })
]xsg;

__DATA__
1 of 10 DOCUMENTS

TITLE HERE

AUTHOR: __________

SUBJECT: ___________________________
____________________________________

BODY: ______________________________
____________________________________
____________________________________
____________________________________

2 of 10 DOCUMENTS

TITLE HERE

AUTHOR: __________

SUBJECT: ___________________________
____________________________________

BODY: ______________________________


3 of 10 DOCUMENTS

TITLE HERE

AUTHOR: __________
__________________

SUBJECT: ________

BODY: ______________________________
____________________________________
____________________________________
____________________________________

[download]

Outputs:

<title> TITLE HERE </title>
<author>  __________ </author>
<subject>  ___________________________
____________________________________ </subject>
<body>  ______________________________
____________________________________
____________________________________
____________________________________ </body>
<title> TITLE HERE </title>
<author>  __________ </author>
<subject>  ___________________________
____________________________________ </subject>
<body>  ______________________________
 </body>
<title> TITLE HERE </title>
<author>  __________
__________________ </author>
<subject>  ________ </subject>
<body>  ______________________________
____________________________________
____________________________________
____________________________________ </body>

[download]
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

In reply to Re^3: Reading chunks of data and then working on it by BrowserUk
in thread Reading chunks of data and then working on it by legend

Title:
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