Gave me a chance to learn opendir and map :-)

opendir LSLRT, "$dir" or die "I hate you, $dir: $!";
# rewinddir not needed
@dir = readdir(LSLRT);
closedir LSLRT; # why 'or die,' if we're all done anyways?
for my $dirent (@dir)
{
 next unless ( -f "$dir/$dirent" );
 $mtime{$dirent} = (stat "$dir/$dirent")[9];
}
my @last_five = (map { $_->[0] }
                 sort { $a->[1] <=> $b->[1] }
                 map { [$_, $mtime{$_} ] }
                 keys %mtime)[-5..-1];
[download]

This is evil because I sort the whole thing and then throw away most of it.

For easy-to-maintain:

my @last_five = chomp (`ls -1 --sort=time`)[0..4];
[download]

Corrections: Don't need to reverse in the ls -1 form, and don't need to rewinndir.

N.B. that I use -1 because CygWin's ls will send ANSI colour codes if I leave it off :-(

opendir LSLRT, "$dir" or die "I hate you, $dir: $!";
my @files = (map { $_->[0] }
                 sort { $a->[1] <=> $b->[1] }
                 map { ( -f and /^F/ )
                      ? [$_, (lstat $_)[9] ] 
                       : () }
                 readdir LSLRT);
closedir LSLRT;
@files = @files[0..($#files > 3 ? 4 : $#files)];
[download]