> grow from right to left instead of shrinking from left to right

This might be much faster if the overlaps are considerably smaller than the total files.

And it avoids any semipredicate problem with $marker.°

(Not heavily tested, please check edge-cases) 

use strict;
use warnings;

my $file1 = join "\n", qw( a b c d c );
my $file2 = join "\n", qw(     c d c x );


my $content = "$file2\n$file1";

$content =~ /^(.*)\n.*\1$/s;



(substr $file2,0,length $1)=$file1;

print $file2;

[download]

a
b
c
d
c
x

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

°) unfortunately it doesn't, prove left to the interested reader

In reply to Re^4: CPAN Module to determing overlap of 2 lists? (updated) by LanX
in thread CPAN Module to determing overlap of 2 lists? by wazat

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.