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

sub match($) {
    my ($Output) = @_;
    for my $match ( @$Output ) {
        if ( $match =~ m/^Routing entry for / ) {
            my @Data = split( ' ', $match );
            my $octet = $Data[ 3 ] ;
            return split( /\./, $octet )
        }
    }
   ()
 }
say "@{[match([split /\n/, <<'END'])]}";
a
b
c
Routing entry for 1.2.3.4
END