I'm not a CS expert, but I think a B-tree might be the right structure (see http://perl.plover.com/BTree/). Pure Perl B-Tree managers are available, such as Tree and Btrees. I think even a Berkeley DB can be stored "in core" with the BerkeleyDB module, and there's a B-Tree version of that.

-- Randal L. Schwartz, Perl hacker

## add a new $nextevent at $time:
push @{$db{$time}}, $nextevent;
## get the lowest event list
keys %db; # reset pointer
my ($time, $events) = each %db; # lowest events
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