#!/usr/bin/perl -w
use strict;
use warnings;

my $line;

while (<DATA>) {
    chomp;

    if (/^$/) {
        print "\n";
        $line = "";
    } elsif (/^[A-Z]{2}:\s/) {
        print "$line\n" if($line);
        $line     = $_;
    } else {
        $line .= " $_";
    }
}

print "$line\n" if($line);

__DATA__
DN: Data Name
Information Sciences
TI: Title
Distribution and abundance of bound volumes of the file in institute
shelves from 1978
AU: Author
Sahu, SR; Gawas, AKG
AF: Affiliation
Inst. of document scanning and documentation profiling at library,
toward the prograssive society and establishment
SO: Source
Test document file. Vol. 5, no. 1, pp. 1-14. Jul 1990.
DE: Descriptors
Article Subject Terms: Abundance; Ecological distribution;
Geographical distribution; Life cycle; Zooplankton; Article Taxonomic
Terms: Euphausia; Article Geographic Terms: ISW,
LA: Language
English