On closer inspection, Bloom::Filter is a bit broken, unless I'm badly misreading it:

* The add() method doesn't actually add anything, because the new() method doesn't initialise the $self->{contents} hashref. it needs to be changed so that either the add method assigns directly to $self->{contents}, or the new() method changes 'keys' to 'contents'. that's probably just a typo.

* because $self->{contents} is not populated, _calculate_filter_length() always returns undef, so the default filter length is always used.

* because $self->{contents} is not populated, build_filter doesn't build a filter anyway.

* the use of == to compare bitstrings in check() is generating warnings, as you've seen. Its purpose is to test that ($a & $b) is the same as $a, ie that all the on bits in $a are also on in $b, and never mind the off bits. Someone better than me at pack(), ie anyone at all, will know how to test equivalence using the bitstrings themselves: meanwhile, you can make it work by testing with the unpacked versions.

* And anyway, it's not incremental. Every time you add a new key, the whole filter is rebuilt by way of a loop on $self->{contents}. This makes it more or less useless for your purposes: you presumably want an iterative check($_) || add($_) mechanism that can be placed in the equivalent of a while(<HUGE_FILE>) loop. As it stands, Bloom::Filter will perform another loop across your whole dataset-so-far for each input line, which might slow things down a bit.

You will need to roll your own, I think, unless the author can be persuaded to accommodate both approaches as well as fixing the bugs, but if you patch Bloom::Filter with this, at least your test script should work:

--- Filter.orig.pm    Tue Apr 20 20:01:37 2004
+++ Filter.pm    Tue Apr 20 20:04:34 2004
@@ -25,7 +25,7 @@
              min_length => 20, 
              filter_length => 20,
              %params, 
-             keys => {}
+             contents => {}
           }, $class;
 }
 
@@ -52,7 +52,7 @@
     my $list = $self->{contents};
     foreach my $add ( @addresses ) {
         # convert email to SHA1 hash if necessary
-        $add = sha1_base64( $add ) if $add =~ /@/o;
+        #$add = sha1_base64( $add ) if $add =~ /@/o;
         $list->{$add}++;
     }
     $self->{reindex_flag} = 1;
@@ -83,7 +83,11 @@
     # A match occurs if every bit we check is on
     foreach my $key ( @keys ) {
         my $mask = $self->_make_bitmask( $key );        
-        push @result, ($mask == ( $mask & $self->{filter} ));
+        #push @result, ($mask == ( $mask & $self->{filter} ));
+
+        my $m = unpack("b*", $mask);
+        push @result, ($m == unpack("b*", ($mask & $self->{filter})))
+;
+        
     }
     return ( wantarray() ? @result : $result[0] );
 }
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