So, overall, this script reads input from $2 or stdin if $2 is not provided, splits it into an array based on the delimiter $2, and then assigns the array to the variable named $1. Note that this script only works in Zsh, not in Bash. Zsh has a more advanced parameter and array system than Bash, so this script can’t be directly translated into Bash.

1. typeset -a: This part declares an array variable.
   • -a flag specifies that the variable is an array.
2. $1=("${(@ps[$2])"${2:-"$(<&0)"}"}"):
   • $1 refers to the first argument passed to the script.
   • "${2:-"$(<&0)"}" is an expansion that evaluates to the second argument passed to the script. If the second argument is not provided, it reads input from standard input (<&0 means read from stdin).
   • "${(@ps[$2])" is an expansion that performs parameter splitting.
   • @ specifies that the expansion should be split into separate array elements.
   • (ps[$2]) is a parameter expansion that performs word splitting on the second argument.
3. The entire expression "${(@ps[$2])"${2:-"$(<&0)"}"}" is wrapped in parentheses and assigned to the variable specified by $1.

In summary, this script takes two arguments: $1 represents the name of the array variable, and $2 represents the values to be assigned to that array. It then assigns the array $2 to the variable named by $1 after performing parameter and word splitting on the second argument. If the second argument is not provided, it reads input from standard input.