use strict;
use warnings;
use feature 'say';

use constant ERR => 1;
use re::engine::TRE 
    max_cost => ERR,
    cost_ins => -1,     # no insertions
    cost_del => -1,     # no deletions
;

my $suffix_source = 'abbaba';
my $prefix_source = 'babbaaaa';

my $max_len = 0;
$prefix_source =~ /^${ \substr $suffix_source, -$_ }/
    and $max_len = $_
    and last 
for reverse ERR + 1 .. length $suffix_source;

say substr( $suffix_source, -$max_len ),
    ' ',
    substr( $prefix_source, 0, $max_len )
if $max_len;

__END__

baba babb