docs: improved the file logic

Author: arteevraina

example_packages/preprocess_fypp/src/file1.fypp

@@ -1,2 +1,15 @@
-#:set LOGLEVEL = 1
-print *, "LOGLEVEL: ${LOGLEVEL}$"
+#: set SHOW = 1
+
+module my_mod1
+  implicit none
+
+    real, parameter :: pi = 3.1415926536  
+    real, parameter :: e = 2.7182818285 
+
+  contains
+
+    subroutine show_consts()
+      print *, "pi = ", pi
+      if (${SHOW}$ == 1) print *, "e = ", e
+    end subroutine show_consts
+end module my_mod1

example_packages/preprocess_fypp/src/file2.fypp

@@ -1,2 +1,15 @@
-#:set LOGLEVEL = 2
-print *, "LOGLEVEL: ${LOGLEVEL}$"
+#: set SHOW = 2
+
+module my_mod2
+  implicit none
+
+    real, parameter :: pi = 3.1415926536  
+    real, parameter :: e = 2.7182818285 
+
+  contains
+
+    subroutine show_consts2()
+      print *, "pi = ", pi
+      if (${SHOW}$ == 1) print *, "e = ", e
+    end subroutine show_consts2
+end module my_mod2