Just try this below code 

#! /usr/bin/perl

use strict;
use warnings;

while (<DATA>) {
        chomp;
        if(/^TAG\d{1}.*TAG\d{1}.*/) {
                print ">>>$_<<\n";
        }
}

__DATA__
TAG1 text one TAG2 etc
TAG1 text two TAG2 etc
TAG1 text three  TAG2 etc
TAGS text four TAG2 etc
TAG1 text five TAGT etc
TAGZ text four TAGX etc

[download]

In reply to Re: negative look behind (again) by leslie
in thread negative look behind (again) by cmic

Title:
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