use strict;
use warnings;
use DB_File;

$DB_BTREE->{'compare'} = sub { $_[0] <=> $_[1] };

tie my %foo, "DB_File", undef, undef, undef, $DB_BTREE;

for (1 .. 10) {
    $foo{$_} = 'value' . $_;
}

while(my($k, $v) = each %foo) {
    print "$k -> $v\n";
}