vim - Apply a set of lines to a template -

i want process set of lines , apply template each line. let's have following block of lines:

case esac if fi 

and following output:

<yyinitial> {case} {     return new symbol(sym.case); }  ...  <yyinitial> {fi} {     return new symbol(sym.fi); } 

so, thought of having template body apply each line, this:

<yyinitial> {###place_holder###} {     return new symbol(sym.###place_holder###); } 

and apply each line.

what thought of selecting lines, putting in register ("a, instance), selecting template putting in register ("b) , call external script generates output. no luck (don't know how pass contents of register external script).

any other approach welcome.

this command job:

:%s/.*/<yyinitial> {&} {\r\treturn new symbol(sym.&);\r}/ 

you remove %, if visual selected lines. create mapping or user command it, if used often.