Something like this perhaps?

...
use List::Util qw{ max };
...
my %filesByAge = map { ( stat $_ )[ 9 ], $_ } glob q{*.rtf};
my $mostRecent = $filesByAge{ max keys %filesByAge };
...
[download]

It might not pick the particular file you want if you have a lot of RTFs created at exactly the same time but that sounds unlikely.

I hope this is helpful.