my( @aFragments, @bFragments );
for my $ai ( 0 .. $#sentences ) {
    my $sa = $sentences[ $ai ];
    my $ua = $uniq[ $ai ];

    for my $bi ( $ai+1 .. $#sentences ) {
        my $sb = $sentences[ $bi ];
        my $ub = $uniq[ $bi ];

        ## process sentence[ $ai ] against sentences[ $bi ]
    }
}