$RID = "MEH|MED|MMD|MMS|CR1|FR1";

open (FIN, "<file.dpf");

my $filecontents = <FIN>;
$filecontents =~ s/($RID)/\n$1/ig;
my @filecontents = split('\n', $filecontents);

my $count = 0;
foreach my $record (@filecontents) {
	print ++$count . "\t$record\n";
}