-my %all_pfx = (%bool_pfx_internal, %bool_pfx_external, %prob_prefix);
-
-sub xpfx { $all_pfx{$_[0]} }
-
-our %PFX2TERM_RMAP;
-my %meta_pfx = (mid => 1, thread => 1, path => 1);
-while (my ($k, $v) = each %all_pfx) {
- $PFX2TERM_RMAP{$v} = $k if $meta_pfx{$k};
-}
+# not documenting m: and mid: for now, the using the URLs works w/o Xapian
+our @HELP = (
+ 's:' => 'match within Subject e.g. s:"a quick brown fox"',
+ 'd:' => <<EOF,
+date range as YYYYMMDD e.g. d:19931002..20101002
+Open-ended ranges such as d:19931002.. and d:..20101002
+are also supported
+EOF
+ 'b:' => 'match within message body, including text attachments',
+ 'nq:' => 'match non-quoted text within message body',
+ 'q:' => 'match quoted text within message body',
+ 'n:' => 'match filename of attachment(s)',
+ 't:' => 'match within the To header',
+ 'c:' => 'match within the Cc header',
+ 'f:' => 'match within the From header',
+ 'a:' => 'match within the To, Cc, and From headers',
+ 'tc:' => 'match within the To and Cc headers',
+ 'bs:' => 'match within the Subject and body',
+ 'dfn:' => 'match filename from diff',
+ 'dfa:' => 'match diff removed (-) lines',
+ 'dfb:' => 'match diff added (+) lines',
+ 'dfhh:' => 'match diff hunk header context (usually a function name)',
+ 'dfctx:' => 'match diff context lines',
+ 'dfpre:' => 'match pre-image git blob ID',
+ 'dfpost:' => 'match post-image git blob ID',
+ 'dfblob:' => 'match either pre or post-image git blob ID',
+);
+chomp @HELP;