TL;DR curl -d 'paste_code="she said wut wut, catsinthebutt"' 'http://pastebin.com/api_public.php'
you have to send a POST to http://pastebin.com/api_public.php with the data you want applied in the 'paste_code' attribute. In this case, "she said wut wut, catsinthebutt" is the thing that will be posted to pastebin.
pipe that to pbcopy on a mac and bam your pastebin url is in your pastebin (yo dawg)
i said wut wut!