diff --git a/t/t5303-pack-corruption-resilience.sh b/t/t5303-pack-corruption-resilience.sh
index b0f5693482..31b20b21d2 100755
--- a/t/t5303-pack-corruption-resilience.sh
+++ b/t/t5303-pack-corruption-resilience.sh
@@ -90,7 +90,7 @@ test_expect_success \
     'create_new_pack &&
      git prune-packed &&
      chmod +w ${pack}.pack &&
-     perl -i -pe "s/ base /abcdef/" ${pack}.pack &&
+     perl -i.bak -pe "s/ base /abcdef/" ${pack}.pack &&
      test_must_fail git cat-file blob $blob_1 > /dev/null &&
      test_must_fail git cat-file blob $blob_2 > /dev/null &&
      test_must_fail git cat-file blob $blob_3 > /dev/null'
@@ -138,7 +138,7 @@ test_expect_success \
     'create_new_pack &&
      git prune-packed &&
      chmod +w ${pack}.pack &&
-     perl -i -pe "s/ delta1 /abcdefgh/" ${pack}.pack &&
+     perl -i.bak -pe "s/ delta1 /abcdefgh/" ${pack}.pack &&
      git cat-file blob $blob_1 > /dev/null &&
      test_must_fail git cat-file blob $blob_2 > /dev/null &&
      test_must_fail git cat-file blob $blob_3 > /dev/null'
diff --git a/t/t9106-git-svn-dcommit-clobber-series.sh b/t/t9106-git-svn-dcommit-clobber-series.sh
index a400dc7966..f8f4718c36 100755
--- a/t/t9106-git-svn-dcommit-clobber-series.sh
+++ b/t/t9106-git-svn-dcommit-clobber-series.sh
@@ -20,8 +20,8 @@ test_expect_success '(supposedly) non-conflicting change from SVN' '
 	test x"`sed -n -e 61p < file`" = x61 &&
 	svn co "$svnrepo" tmp &&
 	cd tmp &&
-		perl -i -p -e "s/^58$/5588/" file &&
-		perl -i -p -e "s/^61$/6611/" file &&
+		perl -i.bak -p -e "s/^58$/5588/" file &&
+		perl -i.bak -p -e "s/^61$/6611/" file &&
 		poke file &&
 		test x"`sed -n -e 58p < file`" = x5588 &&
 		test x"`sed -n -e 61p < file`" = x6611 &&
@@ -40,8 +40,8 @@ test_expect_success 'some unrelated changes to git' "
 test_expect_success 'change file but in unrelated area' "
 	test x\"\`sed -n -e 4p < file\`\" = x4 &&
 	test x\"\`sed -n -e 7p < file\`\" = x7 &&
-	perl -i -p -e 's/^4\$/4444/' file &&
-	perl -i -p -e 's/^7\$/7777/' file &&
+	perl -i.bak -p -e 's/^4\$/4444/' file &&
+	perl -i.bak -p -e 's/^7\$/7777/' file &&
 	test x\"\`sed -n -e 4p < file\`\" = x4444 &&
 	test x\"\`sed -n -e 7p < file\`\" = x7777 &&
 	git commit -m '4 => 4444, 7 => 7777' file &&
diff --git a/templates/hooks--prepare-commit-msg.sample b/templates/hooks--prepare-commit-msg.sample
index aa42acfd68..365242499d 100755
--- a/templates/hooks--prepare-commit-msg.sample
+++ b/templates/hooks--prepare-commit-msg.sample
@@ -22,10 +22,10 @@
 
 case "$2,$3" in
   merge,)
-    perl -i -ne 's/^/# /, s/^# #/#/ if /^Conflicts/ .. /#/; print' "$1" ;;
+    perl -i.bak -ne 's/^/# /, s/^# #/#/ if /^Conflicts/ .. /#/; print' "$1" ;;
 
 # ,|template,)
-#   perl -i -pe '
+#   perl -i.bak -pe '
 #      print "\n" . `git diff --cached --name-status -r`
 #	 if /^#/ && $first++ == 0' "$1" ;;