#!/usr/bin/perl
use strict;
use warnings;
use feature 'say';
use Data::Dumper;

while (<>) {
    chomp;
    if (/[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+/) {
	my @tmp = split /\s+/;
	# print Dumper \@tmp;
	say $tmp[0];
    }
}

__END__

$ perl test.pl in.txt
1.1.1.1:0