use String::CRC32;;
@v = ( chr(0) ) x 256; 
$_ x= 2*1024*1024 for @v;;

sub testAndSet{ 
    my( $hi, $lo ) = ( $_[0] >> 24, $_[0] & 0x00ffffff ); 
    return 1 if vec( $v[$hi], $lo, 1 ); 
    vec( $v[$hi], $lo, 1 )=1; 
    return; 
};;

$n=0; 
testAndSet( crc32( $_, ++$n ) ) and warn "Dup after $n strings" for 'aaaaa'..'zzzzz';;
Dup after 18026 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 18027 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 18042 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 18043 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 18728 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 18729 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 18744 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 18745 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 19378 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 19379 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 116559 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 116574 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 117261 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 117276 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126026 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126027 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126030 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126031 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126042 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126043 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126046 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126047 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126728 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126729 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126732 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126733 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126744 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126745 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126748 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 126749 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 176385 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 176388 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 176389 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 176400 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 176404 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 176405 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 250001 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 250512 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 250513 strings at (eval 12) line 1, <STDIN> line 4.
Dup after 250516 strings at (eval 12) line 1, <STDIN> line 4.