I think your best bet would be to use Perl's match operator, but then again one of the other monks might have a better solution (I'm still learning!). I just setup a little test text file and wrote a few lines of code (below) and it does what you were asking for.

Text file
---------------------------------------
1234567 is alive
12345678 is not alive
123456789 is alive<br><br>

Code
---------------------------------------
#! /usr/bin/perl -w
use strict;

open(FILE, ">test.txt") || die "Unable to open file: $!";
chomp (my @input = <FILE>); # store lines in array, removing CRLF
close(FILE);

foreach my $line (@input) {
   if($line =~ m/is alive/) {
      print "$line\n";
   }
}

Output
-------------------------------------
1234567 is alive
123456789 is alive
[download]

Hope this helps!! -Eric