use strict;
use warnings;


my $time_stamp = qr{^(\w+) (\d+) (\d{2}:\d{2}:\d{2})};

while (<DATA>) {
    next if !(my($mon, $day, $time) = /$time_stamp/);
    next if !(my($interface, $updown) = $' =~ /.*:\seth(\d): link (up|down)/);
    
    if ( $updown eq 'down' ) {
        #... # Process down
        print $time, "\n";
    } 
    else {
        my( $rate, $duplex, $lpa ) = $' =~ /,(\d+)Mbps, ([^,]+), lpa (\w+)/;
        next if !defined($lpa); # Invalid 'up' probably never happens.
        #... # Process up
        print $lpa, "\n";
    }
}

__DATA__
May 03 10:15:21 some text: eth3: link down
May 04 10:16:23 some text: eth3: link up,562Mbps, foos, lpa fum
no time