JavaScript
                  // k          English
var s="string";   // s:"string" s is "string".
s.length===6;     // 6=#s       Is 6 the same as the count of s? (yes)
var s="sub"+s;    // s:"sub",s  s is "sub" concatenated to s.
var x=3;          // x:3        x is 3.
var y=6;          // y:6        y is 6.
s.substring(x,y); // (y-x)#x_s  Take y-x after dropping x of s. ("str")

var d=function(n,s){return s.substring(n,s.length);}   //d:{x_y}
var t=function(n,s){return s.substring(0,s.length-n);} //t:{x#y}
var ss=function(x,y,s){return t(y-x,d(x,s));}          //ss:{t[y-x;d[x,z]]}
ss(x,y,s)===s.substring(x,y);                          //ss[x;y;s]=(y-x)#x_s

var O=function(x){console.log(x);}
 
if(c){t;}else{f;}     // $[c;t;f]   If c then t else f.
var f=function(x){e;} // f:{e}      f is the function defined by e.

confirm("R B");
prompt("R S");

+ plus
* times
- minus
/ divide
% mod

Sources
http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-262.pdf