#! /usr/bin/perl

use strict;
use warnings;

my $t = Tags->new(
  {
    txt_file  => q{text.txt},
    tag_files => [qw{tag1.txt tag2.txt}],
  }
);

my $count = 3;
for (0..$count){
  print $t->output;
}

package Tags;

sub new {
  my $class = shift;
  my $args = shift;
  my $self = {};
  
  die q{no txt file} unless exists $args->{txt_file};
  die q{no tag files} unless exists $args->{tag_files};
    
  my $txt_file = $args->{txt_file};
  open my $fh, q{<}, $txt_file
    or die qq{cant open *$txt_file* to read: $!};
  $self->{txt} = do{local $\;<$fh>};
  
  my @files = @{$args->{tag_files}};
  die q{no tag files} unless @files;
  
  for my $file (@files){
    open my $fh, q{<}, $file
      or die qq{cant open *$file* to read: $!};
    my @lines = <$fh>;
    chomp @lines;
    my ($tag_name) = $file =~ /([^.]+)\./;
    $self->{$tag_name} = \@lines;
  }
  
  bless $self, $class;
  return $self;
  
}

sub output {
  my $self = shift;
  my $txt = $self->{txt};
  $txt =~ s/{{([^}]+)}}/$self->next({tag => $1})/eg;
  return $txt;
} 

sub next {
  my $self = shift;
  my $args = shift;
  my $tag = $args->{tag};
  die q{bad tag} unless exists $self->{$tag};
  my $tag_txt = shift @{$self->{$tag}};
  push @{$self->{$tag}}, $tag_txt;
  return $tag_txt;
}
[download]

Lorem ipsum tag1example1 sit amet, consectetur adipiscing elit. Vestibulum bibendum mi in ipsum tag2example1 id sagittis dolor ultrices. Maecenas vitae nunc diam, quis gravida augue. Integer...

Lorem ipsum tag1example2 sit amet, consectetur adipiscing elit. Vestibulum bibendum mi in ipsum tag2example2 id sagittis dolor ultrices. Maecenas vitae nunc diam, quis gravida augue. Integer...

Lorem ipsum tag1example1 sit amet, consectetur adipiscing elit. Vestibulum bibendum mi in ipsum tag2example3 id sagittis dolor ultrices. Maecenas vitae nunc diam, quis gravida augue. Integer...

Lorem ipsum tag1example2 sit amet, consectetur adipiscing elit. Vestibulum bibendum mi in ipsum tag2example1 id sagittis dolor ultrices. Maecenas vitae nunc diam, quis gravida augue. Integer...

--------------------------

If this is homework and you haven't covered oo yet you may have some explaining to do. :-)

The best? Unlikely. Efficient? Depends. I found it easy to write and, in imo, it reads well so I'll find it easier to maintain. It would also be reasonably easy to extend.

update: In some quarters passing arguments around as hashrefs is considered bad for your health - so be prepared. :-)