Append to existing line

I have a file which has lines that end with a plus (+) sign. I would like to get the next line appended to the one with the plus. For example

bla bla bla bla bla +
blip blip blip 

would become

bla bla bla bla bla blip blip blip

However not all lines end with a plus sign . I would need only those with a plus.

With GNU sed:

$> cat infile
bla bla bla bla bla +
blob blob +
blip blip blip

would become

bla bla bla bla bla blip blip blip
$> sed -e :a -e '/\+$/ {N; s/\n/ /; ta}' infile
bla bla bla bla bla + blob blob + blip blip blip

would become

bla bla bla bla bla blip blip blip
1 Like

Thanks...I was close but I did not place the + sign in the right place.