Easiest way is probably to use strftime from POSIX.pm.

use POSIX 'strftime';

my $today = strftime '%d%m%Y', localtime;

# assume filename is in $name
$name =~ s/(\.\w+)$/$today$1/;
[download]

I'd also recommend using a more meaningful date format (like YYYY-MM-DD) as people from the US often misread DD-MM-YYYY as MM-DD-YYYY for some reason.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you do not talk about Perl club."
-- Chip Salzenberg