I think it would be easier if you used index() because the IP addresses have '.'s in them which mean 'match any character'.

use feature ":5.14";
use warnings FATAL => qw(all);
use strict;
use Data::Dump qw(dump pp);

my $i = "10.0.0.132";  

say for grep {index($_, $i) != -1} split /\n/, << 'END';
a.AS1    10.0.0.128
b.AS1    10.0.0.129
c.AS1    10.0.0.130
d.AS1    10.0.0.131
e.AS1    10.0.0.132
END
[download]

Produces

e.AS1    10.0.0.132