Can you understand it when it's shortened? If you add a comment, can the other people who'll work on the program understand it?

In theory, the fewer lines of code you have, the less bugs. You might want to move sort to the right side of the assignment in the short version, though. :)

opendir(LOGS, '.') or die "Can't open directory: $!"; 
print join("\n", sort map { -M $_ } grep { /\.log/ } readdir(DIR));
closedir(LOGS);
[download]

I'd probably throw a \z anchor at the end of the grep regex, too.