sub re_collapse {
	local $_ = $_[0];

	# explode all collapsed in one go
	s{Re.(\d+).?: } { "Re: " x $1 }ge;

	# re-collapse (no pun intended)
	s{ ( (?:Re:\ ) {2,} ) } { "Re(" . length($1)/4 . "): " }xge;

	return $_;
}