run line question

[ToddAndMargo via perl6-users]

Hi All,

When folks write programs that read the run line like

      xxxx /a abc /r xyz
or
      xxxx /r xyz /a aaabc
or
      dd bs=4096 if=xxx.iso of=/dev/sdc

basically, in any order.

How do they keep track of what goes where?

Many thanks,
-T