#! perl -slw
use strict;

my $pid = open TAIL, '-|', 'tail -f theLog' or die $!;
my @matches;
while( @matched <3 and defined( $_ = <TAIL> ) ) {
      push @matches, $_ if /the search term/;
}

kill 2, $pid;

## do something with the 3 lines in @matches.