how to write value of variable into current edit file in vim script -

i variable's value in vim's script, , how write file i'm editing now.

e.g.

"=== date let todaydate=system("date") 

you can use :put put contents of variable (or expression) current buffer

:put =todaydate 

the :h :put

                                                        :pu :put :[line]pu[t] [x]        put text [from register x] after [line] (default                         current line).  works linewise,                         command can used put yanked block new                         lines.                         cursor left on first non-blank in last                         new line.                         register can '=' followed optional                         expression.  expression continues until end of                         command.  need escape '|' , '"'                         characters prevent them terminating                         command.  example:                                  :put ='path' . \",/test\"                         if there no expression after '=', vim uses                         previous expression.  can see ":dis =". 

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for mappings , editing <c-r>= better :put since allows use expression register , output contents @ cursor location. (take @ :h <c-r>)