You want the Longest common subsequence, not substring. Below a simple modification of the wikipedia pseudocode of the dynamic programming algorithm (http://en.wikipedia.org/wiki/Longest_common_subsequence_problem) to make it word based. 
use strict;
use warnings;

use Data::Dumper;

# word lists, first element a dummy
my @s1 = (q{}, split(/s+/, "Perlmonks is the best perl community"));
my @s2 = (q{}, split(/s+/, "Perlmonks is one of the best community of 
+perl users"));

my @M;

#init dyn. prog. matrix
for my $i ( 0 .. $#s1) {
        $M[$i][0] = 0;
}

for my $i ( 0 .. $#s2) {
        $M[0][$i] = 0;
}

#calc lcs (word based)
for my $i ( 1 .. $#s1) {
        for my $j ( 1 .. $#s2) {
                if ($s1[$i] eq $s2[$j]) {
                        $M[$i][$j] = $M[$i-1][$j-1]+1;
                }
                else {
                        if ($M[$i][$j-1] > $M[$i-1][$j]) {
                                $M[$i][$j] = $M[$i][$j-1];
                        }
                        else {
                                $M[$i][$j] = $M[$i-1][$j];
                        }
                }
        }
}

#print Dumper \@M;
printDiff($#s1, $#s2);

sub printDiff {
        my ($i, $j) = @_;
        if ($i > 0 && $j > 0 and $s1[$i] eq $s2[$j]) {
                printDiff($i-1, $j-1);
                print "  " . $s1[$i];
        }
        else {
                if ($j > 0 && ($i == 0 || $M[$i][$j-1] >= $M[$i-1][$j]
+)) {
                        printDiff($i, $j-1);
                        print " <" . $s2[$j] . ">";
                }
                elsif ($i > 0 && ($j == 0 || $M[$i][$j-1] < $M[$i-1][$
+j])) {
                        printDiff($i-1, $j);
                        print " [" . $s1[$i] . "]";
                }
        }
}

[download]
This outputs: 
 Perlmonks  is <one> <of>  the  best [perl]  community <of> <perl> <us
+ers>

[download]

In reply to Re: diff of two strings by lima1
in thread diff of two strings by flaviusm

Title:
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