Alternately, could make copies of the arrays and add values to the new ones:

```ruby
simd_single = args.dup
simd_single << "--enable-sse" if Hardware.cpu_type == :intel
sing_single << "--enable-altivec" if Hardware.cpu_type == :ppc unless Hardware.cpu_type == :g3 # I'll have better syntax for this soon!

simd_double = args.dup
simd_double << "--enable-sse2" if Hardware.cpu_type == :intel

...

system "./configure", *simd_single # etc.
```