Rewrite case control substitutions

Rewrite case control substitutions, $\, $^, $_
Character case in templates is normally preserved. In addition to preservation of the case of the literal text in a template, note that substitution sequences such as   or     that substitute material extracted from original addresses also preserve the original case of that  material.

When it is desirable to force substituted material to use a particular case, for instance, to force mailboxes to lowercase on UNIX systems, special substitution sequences can be used in templates to force substituted material to a desired case. Specifically,   forces subsequent substituted material into lower case,    forces subsequent substituted material into upper case, and    says to use the original case (as well as turning off  LDAP URL character encoding). So you can use a rule such as unix.domain.com    $\$U$_%unix.domain.com to force mailboxes to lowercase for unix.domain.com addresses.

See also:
 * Rewrite username and subaddress substitutions
 * Rewrite host domain and IP literal substitutions
 * Rewrite LDAP query URL substitutions
 * Rewrite rule template substitutions and control sequences