Heavy lifting is up to you but this is what you’ll use–

• String::Approx
• Algorithm::Diff (splitting on word and then on letter)
• Text::DoubleMetaphone/Text::Phonetic
• Text::Sentence/Lingua::Sentence
• And if you want to go hardcore on the problem: “wordnet”

With your description as given, I'd be hard pushed to come up with any approach; or even rule one out.

I think you would get far better responses if you supplied 3 further pieces of data:

1. A sample template.

   If the real ones are proprietary, makes something up that is consistent with the real thing.

2. A (complete) sample input where the user is "using the template".

   Along with an indication of how far through that sample you would visually determine that they were.

3. A (complete) sample input where the user "is deviating from the template".

   Again, an indication of how much of that you would need to see before visually determining that they were not.

With that, you might get better, more targeted responses.

You may find something of interest in this set of Super Search results: ?node_id=3989;BIT=levenshtein%20distance%20word;BH=0;Wi, perhaps in particular word based levenstein distance path or Levenstein distance transcription.

The basic idea is Levenshtein distance by word rather than by character.

Just pick a reasonable value to test $ratio against (like maybe 1.0):

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1174957

use strict;
use warnings;
use Algorithm::Diff qw(traverse_sequences);

my $template = <<END;
The earliest conceptualization of human rights is credited to ideas ab
+out natural rights emanating from natural law. In particular, the iss
+ue of universal rights was introduced by the examination of extending
+ rights to indigenous peoples by Spanish clerics, such as Francisco d
+e Vitoria and Bartolomé de Las Casas. In the Valladolid debate, Juan 
+Ginés de Sepúlveda, who maintained an Aristotelian view of humanity a
+s divided into classes of different worth, argued with Las Casas, who
+ argued in favour of equal rights to freedom from slavery for all hum
+ans regardless of race or religion. 
END

my $copywitherrors = <<END;
The earliest conceptulization of human rights is credited to ideas abo
+ut rights emanating from natural law. In particular the issue of univ
+ersal rights was introduced by extending rights to indigenous peoples
+ by Spanish clerics, such as Francisco de Vitoria and Bartolomé de La
+s Casas. In the Valladolid debate, Juan Ginés de Sepúlveda, who maint
+ained an Aristotelian view of humanity as divided into clases of diff
+erent worth argued with Las Casas, who argued in favour of equal righ
+ts to freedom from slavery for all humans regardless of race.
END

my $somethingelse = <<END;
Although ideas of rights and liberty have existed in some form for muc
+h of human history, there is agreement that the earlier conceptions d
+o not closely resemble the modern conceptions of human rights. Accord
+ing to Jack Donnelly, in the ancient world, "traditional societies ty
+pically have had elaborate systems of duties... conceptions of justic
+e, political legitimacy, and human flourishing that sought to realize
+ human dignity, flourishing, or well-being entirely independent of hu
+man rights. These institutions and practices are alternative to, rath
+er than different formulations of, human rights".14 The history of hu
+man rights can be traced to past documents, particularly Constitution
+ of Medina (622), Al-Risalah al-Huquq (659-713), Magna Carta (1215), 
+the Twelve Articles of Memmingen (1525), the English Bill of Rights (
+1689), the French Declaration of the Rights of Man and of the Citizen
+ (1789), and the Bill of Rights in the United States Constitution (17
+91) 
END

sub compare
  {
  my ($old, $new) = @_;
  my $changes = 0;

  traverse_sequences( [ split //, $old ], [ split //, $new ],
    {
    DISCARD_A => sub { $changes++ },
    DISCARD_B => sub { $changes++ },
    } );
  return $changes;
  };

my $length = length $template;
print "length: $length\n";

my $answer = compare($template, $copywitherrors);
my $ratio = $answer / $length;
printf "copywitherrors: %d  ratio %.3f\n", $answer, $ratio;

$answer = compare($template, $somethingelse);
$ratio = $answer / $length;
printf "somethingelse: %d  ratio %.3f\n", $answer, $ratio;
[download]

G'day cntrtrst,

"The purpose is to get incoming text streams and compare them to a template ..."

Would this template lend itself to conversion to a regular expression? If so, your comparison might just be "$input =~ /$template_regex/".

[Note: My reply is purely a guess at a solution. As others have already said, better information from you will result in better answers from us. See "How do I post a question effectively?".]