Something like this? 

use strict;
use warnings;
my $text = 'The cat jumped over the dog. Smart cat! He jumped over the
+ dog. The cat jumped over the dog. Smart cat!';
my %seen;
my $longest = '';

while ($text =~ /\s*(.+?[!?.])/g) {
   $longest = $1  if $seen{$1}++ && length $1 > length $longest;
}
print $longest,$/;

[download]

Prints: 

The cat jumped over the dog.

[download]

But it's a whole other challenge if you mean "phrase" and not (terminated) sentence.

In reply to Re: Finding duplicate text in a paragraph by hbm
in thread Finding duplicate text in a paragraph by Jester

Title:
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