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

while(<DATA>) {
	my @tags = ( /(\:TAG\:.*?)[(?=:)]/g );

	for my $tag ( @tags ) {
		print "$tag\n";
	}	
}
__DATA__
:TAG: This is just some text. blahblahblahblahblahblahblah blahblahblah. blahblah?  blah.:TAG: This is just some text. blahblahblahblahblahblahblah blahblahblah. blahblah?  blah. :TAG: This is just some text. blahblahblahblahblahblahblah blahblahblah. blahblah?  blah. :TAG: This is just some more text. blahblahblahblahblahblahblah blahblahblah. blahblah?  blah.