my $when = '2003-07-14 21:39:26.357';
    my ( $yr, $mo, $day, $hr, $min, $sec ) =
        ( $when =~ /(\d{4})(\d\d)(\d\d)(\d\d)(\d\d)(\d\d)/ );
[download]

You have to match all of the punctuation in your source string. E.g., to match

    my $when = '2003-07';
[download]

you would use

    my ($yr,$mo) = $when =~ /^(\d\d\d\d)-(\d\d)/;
                                        ^
[download]

Fixing the complete regex is a variation on this theme.