}
my $dates = join("|", @dates);
-my $match = qr/^${prefix}\d{4}-\d{2}-\d{2}\./;
-my $keep = qr/^${prefix}(?:${dates})\./;
+my $match = qr/^\Q${prefix}\E\d{4}-\d{2}-\d{2}\./;
+my $keep = qr/^\Q${prefix}\E(?:${dates})\./;
opendir(DIR, "$dir") || die "Can't open ${dir}: $!";
-my @files = sort(grep($match, readdir(DIR)));
+my @files = sort(grep(/$match/, readdir(DIR)));
closedir(DIR);