Shell Programming and Scripting

I am using a seed file shown below to separate cisco devices by ios/os type. I want to bunch all the devices based on ios/os version. Once I find a match, I only want to push the ip address into the appropriate array.

Example of seedfile

8 host1 (C3500XL-C3H2S-M) 11.0(5)WC17 10.1.44.21
9 host2 (C3500XL-C3H2S-M) 12.0(5)WC17 10.1.44.22
10 host3 (C3500XL-C3H2S-M) 12.0(5)WC17 10.1.44.23
11 host4 (cat4000-I9K91S-M) 12.2(25)EWA2 10.1.1.20
12 host5 (cat4000-I9K91S-M) 12.2(25)EWA2 10.1.1.21
13 host6 (cat4000-I9K91S-M) 12.2(25)EWA2 10.1.1.22
14 host7 (cat4000-I9K91S-M) 12.2(25)EWA2 10.1.1.23
15 host8 (cat4000-I9K91S-M) 12.2(25)EWA2 10.1.1.24
16 host9 (cat4000-I9K91S-M) 12.2(25)EWA2 10.1.1.25
17 host10 (cat4000-I9K91S-M) 12.2(25)EWA2 10.1.1.26
18 host11 (cat4000-I9K91S-M) 11.2(25)EWA6 10.1.1.27
19 host12 (cat4000-I9K91S-M) 12.2(25)EWA6 10.1.1.28
20 host13 (cat4000-I9K91S-M) 12.2(25)EWA2 10.1.1.29
21 host14 (C3550-I5Q3L2-M) 12.1(22)EA4 10.1.44.5
22 host15 WS-C6506 7.6(8) 10.1.48.10

open (INFILE, "seedfile") or die;
while (<INFILE>) {
chomp($_);
if ($_ =~ /\s\b[5-9]\./) {push(@dos, $_)};
if ($_ =~ /\s\b11\./) {push(@d110, $_)};
if ($_ =~ /\s\b12\.0/) {push(@d120, $_)};
if ($_ =~ /\s\b12\.1/) {push(@d121, $_)};
}
#test to make sure I know whats in "thar"
for ($lindex = 0; $lindex <= $#dos; $lindex++) {
print $dos[$lindex] . "\n";
}
close INFILE;

if $_ meets the requirements, I only want to push the ip address into the "d" arrays. $_[4] <- This obviously doesnt work, but illustrates what it is I want to parse.

This works ... but it just seems that there is a better way ..
if ($_ =~ /\s\b[5-9]\./) {
@ip = split(/ /,$_);
push(@dos, $ip[4])};