Proposed patch:

---
+++
@@ -104,7 +104,7 @@
 		    }
 		} elseif {[regexp {^[ 	]+(.+)} $line {} value] && \
 			[info exists data(key)]} {
-		    append data(mime,$data($key)) " " $value
+		    append data(mime,$data(key)) " " $value
 		} else {
 		    HttpdError $sock 400 $line
 		}

Diff finished.  Fri Jun  7 11:29:42 2019