m4_ifdef(<:_head:$1/$2:>, <:<:##:> m4_indir(<:_head:$1/$2:>)
:>)m4_define(<:_done:$1/$2:>):>):>):>)
+## ADD_HEADER(hdrs)
+##
+## An ACL action to add the given HDRS, which are a `\n'-terminated list of
+## new header lines.
+m4_define(<:ADD_HEADER:>, <:m4_dnl
+ set acl_m_hdradd = ${if def:acl_m_hdradd{$acl_m_hdradd}{}}$1\n:>)
+
## RENAME_HEADERS_ADD(list)
##
## Return a newline-separated list of message header additions of the form