You can get the last file in one go.

$last= (sort { -M $b <=> -M $a } <*.log>)[-1];
[download]

If you have a very large number of files, you may consider using the Schwartzian Transform to minimize sorting time.

$last = (
    map { $_->[0] } 
    sort { $b->[1] <=> $a->[1] } 
    map { [ $_, -M $_ ] } 
    <*.log>
    )[-1];
[download]

Both versions are short enough to be used in a one-liner.

Update
Tested in Linux and Windows. Works fine.