The following uses Algorithm::Diff to do the heavy lifting:

use strict;
use warnings;
use Algorithm::Diff;

my @routes;

local $/ = "\n\n";

push @routes, $_ while $_ = <DATA>;
chomp @routes;

@routes = map {[split "\n"]} @routes;

my @reference = @{shift @routes};
my $lenChanges = 0;
my $hopChanges = 0;

for my $route (@routes) {
    my @diffs = Algorithm::Diff::diff(\@reference, \@$route);

    next if !@diffs;
    @reference != @$route ? ++$lenChanges : ++$hopChanges;
}

print "Length changes: $lenChanges\n";
print "Hop changes:    $hopChanges\n";

__DATA__
13,4.69.137.70
14,4.69.134.70
15,4.69.134.113
16,4.69.135.185
17,4.69.134.246
18,4.68.18.75
19,4.59.0.10
20,124.211.34.129
21,203.181.100.61
22,118.155.197.140
23,124.211.10.66
24,163.139.130.138
25,163.139.124.57
26,202.215.179.1
27,202.215.179.11

13,4.69.137.74
14,4.69.134.70
15,4.69.134.113
16,4.69.135.185
17,4.69.134.246
18,4.68.18.11
19,4.59.0.10
20,124.211.34.121
21,203.181.100.61
22,118.155.197.140
23,124.211.10.66
24,163.139.130.138
25,163.139.124.57
26,202.215.179.1
27,202.215.179.11

13,4.69.137.70
14,4.69.134.78
15,4.69.134.125
16,4.69.135.185
17,4.69.134.250
18,4.68.18.139
19,4.59.0.10
20,124.211.34.121
21,203.181.100.189
22,118.155.197.140
23,124.211.10.66
24,163.139.130.138
25,163.139.124.57
26,202.215.179.1
27,202.215.179.11

13,4.69.137.74
14,4.69.134.70
15,4.69.134.113
16,4.69.135.185
17,4.69.134.246
18,4.68.18.11
19,4.59.0.10
20,124.211.10.120
20,124.211.26.120
21,203.181.100.61
22,118.155.197.140
23,124.211.10.66
24,163.139.130.138
25,163.139.124.57
26,202.215.179.1
27,202.215.179.11
[download]

Prints:

Length changes: 1
Hop changes:    2
[download]

Note too the use of the $/ record separator special variable to ease the parsing of the file into records.