| Hokay, how about
|
| * ^Content-transfer-encoding:[ ]*\/[^ ](.*[^ ])*
|
| This seems to work as intended, grabbing embedded spaces but omitting
| any trailing ones. (I only did a quickie test, though.)
If we may make the bold assumption that there will be at least two characters
in the description of the encoding,
* ^Content-transfer-encoding:.*\/[^ ].*[^ ]
will do the job of stripping exterior whitespace. (Remember that the first
".*" is to the left of "\/" and therefore is stingy.) Otherwise, if methods
of encoding might be named with a single character,
* ^Content-transfer-encoding:.*\/[^ ](.*[^ ])*
or
* ^Content-transfer-encoding:.*\/[^ ](.*[^ ])?