You have to love data files with inconsistent record separators. If you had "\n\n" ie a blank line as the rec sep you could just set $/ = "\n\n" to read a record at a time. You could fix the file format with this:

perl -pi.bak -e 's/--\n/\n/' inconsitent.txt
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You could then just set the input record separator to two newlines and read the data in one record at a time. But you say that the -- is an important part so you need to do something like this:

my @recs;
my $data = '';
while(<DATA>) {
    next unless $data or m/\d+\-\d+/;
    $data .= $_;
    if ( m/^(?:\n|\-\-\n)$/ ) {
        push @recs, $data;
        $data = '';
    }
}
print "$_\n\n\n" for @recs;
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so that you don't lose the -- parts.