Thank you so much Ken! This is amazing. As for your first comment, I might want to compare all the fragments with each other, which is a very hard job. As a work around, I added a (clumsy) piece of code to yours, so that the script picks up the most complete string as the reference one -- meaning the string which contains most words. Here is the code: 
#!/usr/bin/env perl

@exemplars = <DATA>;

foreach $line (@exemplars) {
    @words = split (/\s+/, $line);
    $array[$#words] = $line;
}

@array = sort { $a <=> $b } @array;

$reference = $array[-1];

print "Reference string: $reference";

for (@exemplars) {
    $exemplar = $_;
    s/[.]{3}/.+?/g;
    if ($reference !~ /$_/) {
        print "NO MATCH: $exemplar";
    }
}

__DATA__
Gallia est omnis divisa in partes tres
Gallia est omnis divisa in ...
Gallia est omnis ...
Gallia
... omnis divisa in ...
... in ...
... est ...
Gallia est ... tres
Gallia ... partes tres
Gallia est ... partes tres
Gallia ... divisa ... tres
... tres
quattuor
Gallia ...

[download]
Output is the same as yours. I will run some tests, and see what happens.

In reply to Re^2: Using special characters in left part of a regex match? by shamat
in thread Using special characters in left part of a regex match? by shamat

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.