Csh , how to set var value into new var, in short string concatenation

Shell Programming and Scripting
1

i try to find way to make string concatenation in csh ( sorry this is what i have )
so i found out i can't do :

set string_buff = ""

foreach line("`cat $source_dir/$f`")

$string_buff  = string_buff $line 

end

how can i do string concatenation?

2

Refer to (=read) $var but set (=write) var .
And better no spaces around the = in an assignment. Also csh needs set in an assignment.

set string_buff=""
foreach line ("`cat $source_dir/$f`")
  set string_buff="$string_buff $line"
end

In this simple case the following seems identical

set string_buff="`cat $source_dir/$f`"