use strict;

my %files;
my @files;

@files =<DATA>;
@files = map { s/\n//; $_ } @files;
close(DATA);

foreach (@files) {
    $files{substr($_,0,(length()-4))}++;
}

foreach (keys %files) {
    print "$_ is not matched and has a count of $files{$_}\n" if $files{$_} == 1;
}

__DATA__
001.did
001.mrg
002.did
002.mrg
003.did
004.did
005.did
005.mrg