sed # call sed
" # use double quote so the variable "added_string" gets expanded
/^research:/ # find a line that begins with "research:"
s/$/,$added_string/ # substitute end of line with comma and variable "added_string"
" # end double quote to complete the command
group # in file group
[code]
sed "/^research:/ s/$/,$added_string/" group
[/code/