my $month_abv = qr/[[:upper:]][[:lower:]]{2}/;

my @date_patterns = (
    # Mar 11 2011 08:02:08.32
    ['Mmm DD YYYY HH:MM:SS.uu',
     qr/$month_abv \s+ \d\d? \s+ \d{4} \s+ \d\d:\d\d:\d\d\.\d\d /x],

    # Mar 11 2011 08:02:08
    ['Mmm DD YYYY HH:MM:SS',
     qr/$month_abv \s+ \d\d? \s+ \d{4} \s+ \d\d:\d\d:\d\d       /x],

    # Mar 11 08:02:08.32
    ['Mmm DD HH:MM:SS.uu',
     qr/$month_abv \s+ \d\d? \s+ \d\d:\d\d:\d\d\.\d\d           /x],

    # Mar 11 08:02:08
    ['Mmm DD HH:MM:SS',
     qr/$month_abv \s+ \d\d? \s+ \d\d:\d\d:\d\d                 /x],
);

my $line = q{
    Mar 11 08:02:08 172.28.17.253 Mar 11 2011 08:02:08 D+R-FW-1 :
    Jan 1 2011 00:00:00.07;
};

DATE: until ($line =~ /\G\z/gc) {
    foreach my $pat (@date_patterns) {
        my($form, $re) = @$pat;
        if ($line =~ /\G\b($re)\b/gc) {
            say "Matching date form '$form': $1";
            next DATE;
        }
    }
    $line =~ /./sgc; # no matches, bumpalong
}