diff --git a/lttb.awk b/lttb.awk
index 86085d3..7613945 100644
--- a/lttb.awk
+++ b/lttb.awk
@@ -80,12 +80,12 @@ function expreval(expr,  valbuf, c, prevc, i, l) {
         stackpush(VALSTACK, norm(valbuf))
         valbuf = ""
       }
-      if(substr(toupper(expr), i+1, 3) == "RND") {
+      if(substr(expr, i+1, 3) == "RND") {
         stackpush(VALSTACK, 0)
         c = "$"
         i += 2        
       }
-      if(c ~ /[a-zA-Z]/) stackpush(VALSTACK, norm(VARS[toupper(c)]))
+      if(c ~ /[A-Z]/) stackpush(VALSTACK, norm(VARS[c]))
       else if(c == "(") stackpush(OPSTACK, "(")
       else if(c == ")") {
         while(stacktop(OPSTACK) != "(" && alen(OPSTACK) > 0) evalhelper()
@@ -113,7 +113,7 @@ function do_GOS(stmt) {stackpush(CALLSTACK, IP); do_GO(stmt)}
 function do_RE(stmt) {IP = stackpop(CALLSTACK)}
 
 function do_LE(stmt,  vname, eqp, expr) {
-  vname = toupper(substr(stmt, 1, 1))
+  vname = substr(stmt, 1, 1)
   if(vname ~ /[A-Z]/) {
     eqp = index(stmt, "=")
     expr = substr(stmt, eqp + 1)
@@ -136,7 +136,7 @@ function do_IF(stmt,  ropos, roend, relop, thenpos, rest, restpos, kw, expr1, ex
   thenpos = 0
   for(k=1; k<=10; k++) {
     kw = IF_KWS[k]
-    thenpos = index(toupper(rest), kw)
+    thenpos = index(rest, kw)
     if(thenpos > 0) {
       if(kw == "=") thenpos--
       restpos = thenpos
@@ -160,13 +160,13 @@ function do_IF(stmt,  ropos, roend, relop, thenpos, rest, restpos, kw, expr1, ex
 
 function do_IN(stmt,  v, i, l) {
   gsub("[[:space:]]+", "", stmt)
-  l = split(stmt, varlist, ",")
+  l = split(toupper(stmt), varlist, ",")
   printf "? "
   inputstr = ttyinput()
   gsub("[[:space:]]+", "", inputstr)
   split(toupper(inputstr), inputlist, ",")
   for(i=1;i<=l;i++) {
-    v = toupper(substr(varlist[i], 1, 1))
+    v = substr(varlist[i], 1, 1)
     VARS[v] = expreval(inputlist[i])
   }
 }
@@ -206,7 +206,7 @@ function do_EN(stmt) {IP = -1; split("", CALLSTACK)}
 
 # Program line execution function
 function progexec(stmt,  kw, ws, body) {
-  kw = toupper(substr(stmt, 1, 2))
+  kw = substr(stmt, 1, 2)
   if(substr(kw, 2, 1) == "=") {
     kw = "LE"
     stmt = "LE " stmt
@@ -217,7 +217,7 @@ function progexec(stmt,  kw, ws, body) {
     if(ws > 0) body = wstrim(substr(stmt, ws))
     else body = ""
     if(kw == "GO") {
-      if(substr(toupper(stmt), 3, 1) == "S") do_GOS(body)
+      if(substr(stmt, 3, 1) == "S") do_GOS(body)
       else do_GO(body)
     } else if(kw == "LE") do_LE(body)
     else if(kw == "IF") do_IF(body)
@@ -240,7 +240,7 @@ function proginput(stmt,  lno, i, l, c) {
   }
   stmt = substr(stmt, i+1)
   if(lno > 0) PROGMEM[lno] = stmt
-  else if(index(toupper(stmt), "REM") != 1) progexec(stmt)
+  else if(index(stmt, "REM") != 1) progexec(stmt)
 }
 
 # Clearing action
@@ -259,8 +259,8 @@ function ext_LOAD(fname,    err, s) {
     print "Error: File " fname " does not exist or cannot be read."
     return
   }
-  if(err > 0) proginput(wstrim(s))
-  while((getline s < fname) > 0) proginput(wstrim(s))
+  if(err > 0) proginput(toupper(wstrim(s)))
+  while((getline s < fname) > 0) proginput(toupper(wstrim(s)))
   close(fname)
 }
 
@@ -279,7 +279,7 @@ function ext_LIST(fname,  i, sep) {
 
 function ext_RUN() {
   for(IP = 1; IP > 0 && IP < 32768; IP++)
-    if(IP in PROGMEM && length(PROGMEM[IP]) > 0 && index(toupper(PROGMEM[IP]), "REM") != 1)
+    if(IP in PROGMEM && length(PROGMEM[IP]) > 0 && index(PROGMEM[IP], "REM") != 1)
       progexec(PROGMEM[IP])
 }
 
@@ -306,17 +306,17 @@ BEGIN {
 END {
   while(1) {
     printf "> "
-    cmd = wstrim(ttyinput())
+    cmd = toupper(ttyinput())
     if(length(cmd) > 0) {
-      if(toupper(cmd) == "BYE") {print "Bye!"; break}
-      else if(toupper(cmd) == "RUN") ext_RUN()
-      else if(toupper(cmd) == "LIST") ext_LIST("")
-      else if(toupper(cmd) == "NEW" || toupper(cmd) == "CLEAR") ext_CLEAR()
-      else if(toupper(cmd) == "LOAD") {
+      if(cmd == "BYE") {print "Bye!"; break}
+      else if(cmd == "RUN") ext_RUN()
+      else if(cmd == "LIST") ext_LIST("")
+      else if(cmd == "NEW" || cmd == "CLEAR") ext_CLEAR()
+      else if(cmd == "LOAD") {
         printf "File name: "
         ext_LOAD(ttyinput())
       }
-      else if(toupper(cmd) == "SAVE") {
+      else if(cmd == "SAVE") {
         printf "File name: "
         ext_LIST(ttyinput())
       }
diff --git a/test.bas b/test.bas
index ea7235a..8d3d63c 100644
--- a/test.bas
+++ b/test.bas
@@ -1,4 +1,6 @@
 5   rem This is a comment and should never be executed
+
+9   rem Program loaders should ignore empty lines correctly
 10  print "Luxferre's Truly Tiny BASIC test suite"
 15  print ""
 20  print "All lines should end with OK to pass"