Programming :: Using Sed Command Twice On One File?

what i have is a list of words 6 to a line im trying to use the sed command to insert a comma in between each word and at the end of the last one

[code]....

the last line of the variable does not have 6 words what i have so far is this

Code:

words=`cat /usr/share/dict/words |grep "^[$list]*$" | xargs -n 6 echo | sed -e 's/[ ]+/,/g s/$/,/g'`

it dosent work though i originally started off with

Code:

words=`cat /usr/share/dict/words |grep "^[$list]*$" | xargs -n 6 echo | sed -e 's/[ ]+/,/g' this puts a comma inbetween them but takes out the space and dosent put a comma at the end of the line.. basicaly what i needed to know is how i could you multiple sed commands to fix this