2.13 Positional Operators in the RHS

The RHS rewrites by substitution. Wildcard operators in the LHS select the portions of the workspace to be passed to the RHS. The first wildcard is assigned to $1 , the second to $2 , and so on. Consider:

R$+@$*    $2!$1      

$1

 

$2

Here, an Internet address is rewritten in UUCP form. Note that there are only nine such positional operators, and that $0 is illegal.