http://www.perlmonks.org?node_id=308417

revdiablo has asked for the wisdom of the Perl Monks concerning the following question:

Hello good Monks. First let me start out with the problem: given an arbitrary list of strings, find the longest common substring. My approach to this problem is to grab one of the strings from the list, scan through it with successively decreasing substring lengths, and check the list for matches. This is simple, and seems quite effective, but I'm wondering if there are any problems with this approach? Could it be done simpler and more efficiently? Is there a well-known algorithm to do this, and I am too daft to find it?

Here is the working code I came up with. I do not have any particular problem with this code, I just wanted to run it by the Monastery to see if anyone could give me suggestions, or find any lurking problems:

```#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;

for ([ qw(fooabc123 fooabc321 foobca232) ],
[ qw(abcfoo123 bcafoo321 foo123abc) ],
[ qw(foo bor boz bzo) ]) {

print Dumper(\$_);
print findlcs(@{ \$_ }), "\n";
print "---\n";
}

sub findlcs {
my \$substr = \$_[0];
my \$len = length \$_[0];
my \$off = 0;

while (\$substr) {
my @matches = grep /\Q\$substr/, @_;
#printf "%s%-".(length(\$_[0])-\$off)."s matches %d\n",
#       " " x \$off, \$substr, scalar @matches;

last if @matches == @_;

\$off++;
\$len-- and \$off=0 if \$off+\$len > length \$_[0];

\$substr = substr \$_[0], \$off, \$len;
}

return \$substr;
}