$ perl -e 'my $foo = "Hello WorldFoo BarPerl MonksSlash Dot"; my @x = 
+split /(?<=[a-z])(?=[A-Z])/, $foo; print map("[$_]",@x),$/'
[Hello World][Foo Bar][Perl Monks][Slash Dot]
[download]

Using look-behind and look-ahead tags, you end up matching a zero-width point between characters as your split point.

(PS - "bad at regexps"? I find look-behind and look-ahead are relatively rarely used, so it's just a matter of experience - and my experience on this has solely been answering questions here ;->)