Because of the way that hashes are stored in memory, the order of keys returned is not guaranteed to be ordered or even consistent. If you want to get the lowest key, then something like...

my @ordered_list = sort keys %myhash;

...will put the lowest key (sorted asciibetically) into the $ordered_list[0] element. See this and this for futher info on sort and keys.

Hope this helps.

Elgon

Update: Or you could use Foxcub's far more elegant solution!