The following pure-Perl implementation of Longest Common Sub String outstrips even the advanced algorithm used by String::LCSS_XS:

#! perl -slw
use strict;
use Time::HiRes qw[ time ];

sub lcssN (\$\$;$) {
    my( $ref1, $ref2, $min ) = @_;
    my( $swapped, $l1, $l2 ) = ( 0, map length( $$_ ), $ref1, $ref2 );
    ( $l2, $ref2, $l1, $ref1, $swapped ) = ( $l1, $ref1, $l2, $ref2, 1
+ ) if $l1 > $l2;
    $min = 1 unless defined $min;

    my $mask = $$ref1 x ( int( $l2 / $l1 ) + 1 );

    my @match = '';
    for my $start ( 0 .. $l1-1 ) {
        my $masked = substr( $mask, $start, $l2 ) ^ $$ref2;
        while( $masked =~ m[\0{$min,}]go ) {
            @match = (
                substr( $$ref2, $-[ 0 ], $+[ 0 ] - $-[ 0 ] ),
                ( $-[ 0 ]+$start ) % $l1,
                $-[ 0 ]
            ) if ( $+[ 0 ] - $-[ 0 ] ) > length $match[ 0 ];
        }
    }
    @match[ 2, 1 ] = @match[ 1, 2 ] if $swapped;
    return unless $match[ 0 ];
    return wantarray ? @match : $match[ 0 ];
}

our $MIN //= 10;
my $start = time;

my( @labels, @strings );
while( <> ) {
    push @labels, $_;
    push @strings, scalar <>;
}

chomp @labels; chomp @strings;

for my $i ( 0 .. $#strings ) {
    for my $j ( $i+1 .. $#strings ) {
        my( $m, $o1, $o2 ) = lcssN( $strings[ $i ], $strings[ $j ], $M
+IN );
        next unless defined $m;
        printf "%s(%d) and %s(%d): %d '%s'\n",
             $labels[ $i ], $o1,
             $labels[ $j ], $o2,
             length( $m ), $m;
    }
}

printf "Took: %.3f seconds\n", time() - $start;

__END__
## The script above
c:\test>perl -s lcssn.pl -MIN=10 -- junk90.dat 
000001(37) and 000002(872): 127 '5808821137152553645216516684787076304
+368738347768274782252043367265484547586755564151615422250715355234473
+558428710868782135070'
000008(550) and 000089(355): 10 '3252367176'
000040(219) and 000081(623): 11 '61341721171'
000046(808) and 000056(845): 12 '876526361506'
000058(837) and 000069(276): 11 '00666788082'
Took: 12.494 seconds

## A similar script that uses String::LCSS_XS on the same file
c:\test>lcss10 junk90.dat
000001(37) and 000002(872): 127 '5808821137152553645216516684787076304
+368738347768274782252043367265484547586755564151615422250715355234473
+558428710868782135070'
000008(550) and 000089(355): 10 '3252367176'
000040(219) and 000081(623): 11 '61341721171'
000046(808) and 000056(845): 12 '876526361506'
000058(837) and 000069(276): 11 '00666788082'
Took: 14.577 seconds
[download]

If I were to package this up for CPAN, the obvious namespace would be String::LCSS, especially as that module is fundamentally broken, hasn't been updated in 6 years and has outstanding bugs going back 4 years.

However, getting module maintainers to accept NIH code is fraught with frustrations; the procedure (what is that again?), for taking over maintenance of existing packages seems to be equally so.

So, what to do? Upload it as an unauthorised version? Under a different namespace? Suffer the frustrations?