thank you all for your responses....i've fashioned some code as follows into a separate script that runs as the first script in a pipeline, e.g. perl pre_script <bibfile | perl processing_script. this nicely separates the complex/multipath processing away from the multiline problem. I know i could have been more concise...but this problem was all about converting the data to get a job done; not to make pretty code. Thanks once again....+es all round.

while($line=<>) {
        chomp $line;
        if($line=~/^\*\*\* DOCUMENT BOUNDARY \*\*\*/) {
                check();
                print "$line\n";
                next;
        }
        if($line=~/^FORM=/) {
                check();
                print "$line\n";
                next;
        }
        if($line=~/\.\d\d\d\./) {
                check();
                $started_tag = 1;
        }
        $tag.=$line;
}

sub check() {
        if($started_tag) {
                print "$tag\n";
                undef $tag;
                $started_tag = 0;
        }
}
[download]