Update How.md

Author: Archips

level04/resources/How.md

@@ -19,7 +19,7 @@ sub x {
 }
 x(param("x")); 
 ```
-**sub x** define a subroutine. In it, there's a variable **y** that takes the value of the first argument of the function. The back ticks mean for **print** that it has to execute the shell command `echo $y 2>&1` instead of print `echo $y 2>&1`. So we can conclude that **y** aka the first param will be executed. So the idea in this case is to pass `getflag` as argument to the **x** subroutine. To do so, we'll use that command:
+**sub x** defines a subroutine. In it, there's a variable **y** that takes the value of the first argument of the function. The back ticks mean for **print** that it has to execute the shell command `echo $y 2>&1` instead of print `echo $y 2>&1`. So we can conclude that **y** aka the first param will be executed. So the idea in this case is to pass `getflag` as argument to the **x** subroutine. To do so, we'll use that command:
 
 `curl 'localhost:4747?x=$(getflag)'`  gives us **`ne2searoevaevoem4ov4ar8ap`**