+ # handle filename*=ISO-8859-1''%74%E9%73%74%2E%74%78%74, parameter value
+ # continuations, and similar syntax from RFC 2231
+ if ($field =~ /^Content-(Type|Disposition)/i) {
+ # This concatenates continued parameters and normalizes encoded params
+ # to QB encoded-words which we handle below
+ $str = MIME::Field::ParamVal->parse($str)->stringify;
+ }
+
+ # Pre-parse by removing all whitespace between encoded words
+ my $encoded_word = qr/
+ =\? # =?
+ ([^?]+?) # charset
+ (?:\*[^?]+)? # optional '*language'
+ \? # ?
+ ([QqBb]) # encoding
+ \? # ?
+ ([^?]+) # encoded string
+ \?= # ?=
+ /x;
+ $str =~ s/($encoded_word)\s+(?=$encoded_word)/$1/g;
+
+ # Also merge quoted-printable sections together, in case multiple
+ # octets of a single encoded character were split between chunks.
+ # Though not valid according to RFC 2047, this has been seen in the
+ # wild.
+ 1 while $str =~ s/(=\?[^?]+\?[Qq]\?)([^?]+)\?=\1([^?]+)\?=/$1$2$3?=/i;
+
+ # XXX TODO: use decode('MIME-Header', ...) and Encode::Alias to replace our
+ # custom MIME word decoding and charset canonicalization. We can't do this
+ # until we parse before decode, instead of the other way around.
+ my @list = $str =~ m/(.*?) # prefix
+ $encoded_word
+ ([^=]*) # trailing
+ /xgcs;