$DB_BTREE->{'flags'} = R_DUP;
$DB_BTREE->{'compare'} = \&_compare;
my %btree;
my $bhandle = tie %btree, 'DB_File', undef, O_RDWR|O_CREAT, 0640, $DB_HASH;

my $len = 26;
my @array =  ( 'a'..'z' );
foreach ( 1..$len ) {
    $btree{$_} = shift @array;
}
# add a second value to each so that each key has duplicate values
@array =  ( 'A'..'Z' );
foreach ( 1..$len ) {
    $btree{$_} = shift @array;
}

# test to see that each value is printed from 20 - end
my @v = $bhandle->get_dup(20);
print "v is @v 20\n";

while( $bhandle->seq($k,$v, R_NEXT) == 0 ) {
    my @v = $bhandle->get_dup($k);
    print "$k @v\n";
}

# now associate a single value with a key

$btree{22.5} = 'HHI';

# test to see that each value is printed from 20 - end
my @v = $bhandle->get_dup(20);
print "v is @v 20\n";

while( $bhandle->seq($k,$v, R_NEXT) == 0 ) {
    my @v = $bhandle->get_dup($k);
    print "$k @v\n";
}
# 22.5 does not show up

# add a second value for 22.5
$btree{22.5} = 'JKL';

# test to see that each value is printed from 20 - end
my @v = $bhandle->get_dup(20);
print "v is @v 20\n";

while( $bhandle->seq($k,$v, R_NEXT) == 0 ) {
    my @v = $bhandle->get_dup($k);
    print "$k @v\n";
}

# now 22.5 is in the list