Expanding arrays in method calls - why the restriction?

I can do

a = %w(foo bar baz)
system('rm', *a)

However, I can't do

opts = %w(--si --summarize)
system('du', *opts, '/tmp')

which seems to me like a reasonable thing to want to do.

Is there some technical reason why the * parameter has to be the last 
one in the argument list, given that the array must be of finite size 
anyway, and presumably it gets expanded out in the process so that the 
receiver doesn't know an array was involved?


mathew