Shell Programming and Scripting

I know there are other ways of accomplishing the below task, but the purpose of this thread is to understand the below code.

I wanted to use xargs with user defined function in korn shell. Am aware, that I could write custom function into a script and place it in FPATH and then call it in xargs, but I wanted to have it all in the same shell script. Bash isnt an option for me at the moment. After 2-3 days of searching, I found the solution which works, but am unable to understand a part of it..

Code:

cat ordernum.txt | xargs -P 25 -n 1 ksh -c '
  function fun { 
    do some processing
  } 
  shift "$1" 
  fun "$@"' 2 1

Can someone help me with the last two lines of the code.

Thanks a ton.

shift moves the parameters so that $2 is now $1,etc.
$@

Code:

> cat test.sh
shift "$1"
echo "$@" 2 1

> test.sh 1 2 3 4 5 6 7 8 9
2 3 4 5 6 7 8 9 2 1

> test.sh 1
2 1

> test.sh 1 2
2 2 1

I was thinking, it would go into endless loop, as the function "fun" is being declared and at the end it being called as well.. within the function