G'day seismofish,

Welcome to the Monastery (at least with respect to posting).

You can use constants to avoid:

• The need to reference capture variables; e.g. ($1,$2,$3,$4,$5,$6,$7).
• The need to declare and define a list of variables; e.g. ( $mon, $day, $time, $interface, $rate, $duplex, $lpa ).
• The use of named captures requiring a multitude of ?<NAME> added to your regexes.

Here's an example:

#!/usr/bin/env perl

use strict;
use warnings;

use constant {
    MON       => 0,
    DAY       => 1,
    TIME      => 2,
    INTERFACE => 3,
    RATE      => 4,
    DUPLEX    => 5,
    LPA       => 6,
};

use Test::More tests => 12;

my $re_dn = qr{^(\w+) (\d+) (\d{2}:\d{2}:\d{2}) .*: eth(\d): link down
+};
my $re_up = qr{^(\w+) (\d+) (\d{2}:\d{2}:\d{2}) .*: eth(\d): link up, 
+(\d+)Mbps, ([^,]+), lpa (\w+)};

my @logs = (
    'May 19 13:58:01 foo: eth0: link down',
    'May 19 13:58:11 foo: eth0: link up, 100Mbps, bar, lpa quux',
    '# some comment in the logfile',
);

for (@logs) {
    my @matches;

    if (@matches = /$re_dn/) {
        is $matches[MON], 'May';
        is $matches[DAY], 19;
        is $matches[TIME], '13:58:01';
        is $matches[INTERFACE], 0;
    }
    elsif (@matches = /$re_up/) {
        is $matches[MON], 'May';
        is $matches[DAY], 19;
        is $matches[TIME], '13:58:11';
        is $matches[INTERFACE], 0;
        is $matches[RATE], 100;
        is $matches[DUPLEX], 'bar';
        is $matches[LPA], 'quux';
    }
    else {
        is 0+@matches, 0;
    }
}
[download]

Output:

1..12
ok 1
ok 2
ok 3
ok 4
ok 5
ok 6
ok 7
ok 8
ok 9
ok 10
ok 11
ok 12
[download]