I use this function to create "timestamp" names suitable for backup filenames - names that are easily sorted, and unique.

The full script can be found here.

sub newname {
    my @t = reverse((localtime)[0..5]); 
    $t[0]+=1900; $t[1]++;     
    my $newbackup =
        sprintf("%4u-%02u-%02u-%02u-%02u-%02u_000",@t).'.zip';
    $newbackup =~ s/(\d\d\d)\.zip$/substr('00'.($1+1),-3).'.zip'/e 
        while (-e $newbackup);
    return $newbackup;
}
[download]

HTH

Update: Minor code tidy for sake of clarity