#!/usr/bin/perl

use strict;
use warnings;

# https://perlmonks.org/?node_id=11148806

my $text = 'This is arbitrary just an arbitrary just example of text just arbitrary.';

@_ = qw( ju.. arb.{1,4}ary );

$text =~ m/
	(?:(?:This)|(?:That))
	.*? (??{ $_[ 0 ] })
	.*? (??{ $_[ 1 ] })
	/x and
	$text =~ s/
	(??{ "(*FAIL)" x ! @_ })
	.*? \K ( (??{ $_[ 0 ] }) ) (?{ shift @_ })
	/<<<$1>>>/gx;

print $text, "\n";

##</code><code>##

This is arbitrary <<<just>>> an <<<arbitrary>>> just example of text just arbitrary.