#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my $info;
$info .= $_ while(<DATA>);
my %lines;

while($info =~ m/(?:^|\n)(\d+)\:(.+?)(?=(?:\n\d)|$)/gs) {
  $lines{$1} = $2;
}

print Dumper (\%lines);

__DATA__
3: Tag <test> found
Tag <test> found
5: Tag <test> found
7: Tag <test> found
14: Tag <test> found
16: Tag <test> found
18: Tag <test> found
21: Tag <test> found
25: Tag <test> found
27: Tag <test> found
29: Tag <test> found
32: Tag <test> found
34: Tag <test> found
49: Tag <test> found
80: Tag <test> found
98: Tag <test> found
Tag <test> found