use strict;

my @sorted = map { $_->[0] } sort { $a->[1] <=> $b->[1] }
    map {
        chomp( my $x = $_ ); s!\D+!!g; [ $x, $_ ]
    } <DATA>;

# for your case, we just pop() off the last element
# (which would be the current log) and handle the rest!
my $current = pop( @sorted );
warn( "$current is newest logfile, not touching it!\n" );

for my $log ( @sorted ) {
    # unlink( '/var/logs/' . $log; # or whatever
}

__DATA__
access_log_04_05_20_03_00_00
access_log_04_05_20_03_30_00
access_log_04_05_20_03_30_01
access_log_04_05_20_03_29_30
access_log_03_05_19_03_30_00
access_log_04_05_17_03_30_00
access_log_04_04_20_03_30_00
access_log_04_05_20_03_31_00