2.12 Wildcard Operators in the LHS

The LHS of a rule is compared to an address or to the result of rewriting by earlier rules. The comparison is case insensitive. To illustrate, consider passing the address [email protected] to this LHS:

$* @ $+ .ORG

The $* (match zero or more) will match hat , the @ will match exactly, the $+ (match one or more) will match coat , and the .ORG will match .org despite the case difference.

Wildcard operators match as little as possible in order to make the entire LHS match. For an address like a@b@c , the LHS $*@$+ will cause the $* to match the a .

$*

Matches zero or more tokens. Prefers zero, or the fewest possible, to satisfy an LHS match.

$+

Matches one or more tokens. Prefers one, or the fewest possible, to satisfy an LHS match.

$-

Matches exactly one token.

$@

Matches exactly zero tokens.

$=

Matches any word in a class. Words may be single-token (like coat ) or multi-token (like coat.org ).

$~

Matches any single token not in a class.