You can access items in an array with negative indices:

my @list = `dir *.log \/B \/OD`;
my $newest = $list[-1];
print "$newest\n";
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Some people dislike shelling out, though. You could use readdir, sort, and the -X filetest operators to check timestamps. I think it'd look something like this:

my @files = sort { -M $a <=> -M $b } <*.log>;
my $newest = $files[-1];
print "$newest\n";
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That's untested, though, since it's late and I don't run Windows.