diff --git a/clang/test/make_test_dirs.pl b/clang/test/make_test_dirs.pl
--- a/clang/test/make_test_dirs.pl
+++ b/clang/test/make_test_dirs.pl
@@ -1,9 +1,10 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 #
 # Simple little Perl script that takes the cxx-sections.data file as
 # input and generates a directory structure that mimics the standard's
 # structure.
 use English;
+use warnings;
 
 $current_indent_level = -4;
 while ($line = <STDIN>) {
diff --git a/clang/tools/scan-build/bin/set-xcode-analyzer b/clang/tools/scan-build/bin/set-xcode-analyzer
--- a/clang/tools/scan-build/bin/set-xcode-analyzer
+++ b/clang/tools/scan-build/bin/set-xcode-analyzer
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/env python
 
 # [PR 11661] Note that we hardwire to /usr/bin/python because we
 # want to the use the system version of Python on Mac OS X.
diff --git a/clang/utils/TestUtils/pch-test.pl b/clang/utils/TestUtils/pch-test.pl
--- a/clang/utils/TestUtils/pch-test.pl
+++ b/clang/utils/TestUtils/pch-test.pl
@@ -1,10 +1,11 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 
 # This tiny little script, which should be run from the clang
 # directory (with clang in your patch), tries to take each
 # compilable Clang test and build a PCH file from that test, then read
 # and dump the contents of the PCH file just created.
 use POSIX;
+use warnings;
 
 $exitcode = 0;
 sub testfiles($$) {
diff --git a/clang/utils/analyzer/reducer.pl b/clang/utils/analyzer/reducer.pl
--- a/clang/utils/analyzer/reducer.pl
+++ b/clang/utils/analyzer/reducer.pl
@@ -1,5 +1,6 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 use strict;
+use warnings;
 use File::Temp qw/ tempdir /;
 my $prog = "reducer";
 
@@ -31,8 +32,9 @@
 my $commandStr = "@$command";
 
 print OUT <<ENDTEXT;
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 use strict;
+use warnings;
 my \$BAD = 1;
 my \$GOOD = 0;
 `rm -f $reduceOut`;
diff --git a/clang/utils/analyzer/update_plist_test.pl b/clang/utils/analyzer/update_plist_test.pl
--- a/clang/utils/analyzer/update_plist_test.pl
+++ b/clang/utils/analyzer/update_plist_test.pl
@@ -1,5 +1,6 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 use strict;
+use warnings;
 require File::Temp;
 use File::Temp ();
 
diff --git a/clang/www/demo/index.cgi b/clang/www/demo/index.cgi
--- a/clang/www/demo/index.cgi
+++ b/clang/www/demo/index.cgi
@@ -1,4 +1,4 @@
-#!/usr/dcs/software/supported/bin/perl -w
+#!/usr/dcs/software/supported/bin/perl
 # LLVM Web Demo script
 #
 
@@ -6,6 +6,7 @@
 use CGI;
 use POSIX;
 use Mail::Send;
+use warnings;
 
 $| = 1;
 
diff --git a/debuginfo-tests/llgdb-tests/test_debuginfo.pl b/debuginfo-tests/llgdb-tests/test_debuginfo.pl
--- a/debuginfo-tests/llgdb-tests/test_debuginfo.pl
+++ b/debuginfo-tests/llgdb-tests/test_debuginfo.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 #
 # This script tests debugging information generated by a compiler.
 # Input arguments
diff --git a/lldb/docs/use/python-reference.rst b/lldb/docs/use/python-reference.rst
--- a/lldb/docs/use/python-reference.rst
+++ b/lldb/docs/use/python-reference.rst
@@ -607,7 +607,7 @@
 
 ::
 
-  #!/usr/bin/python
+  #!/usr/bin/env python
 
   import lldb
   import commands
@@ -715,7 +715,7 @@
 
 ::
 
-  #!/usr/bin/python
+  #!/usr/bin/env python
 
   import lldb
   import os
diff --git a/lldb/scripts/disasm-gdb-remote.pl b/lldb/scripts/disasm-gdb-remote.pl
--- a/lldb/scripts/disasm-gdb-remote.pl
+++ b/lldb/scripts/disasm-gdb-remote.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 use strict;
 
diff --git a/llvm/utils/GenLibDeps.pl b/llvm/utils/GenLibDeps.pl
--- a/llvm/utils/GenLibDeps.pl
+++ b/llvm/utils/GenLibDeps.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 #
 # Program:  GenLibDeps.pl
 #
diff --git a/llvm/utils/codegen-diff b/llvm/utils/codegen-diff
--- a/llvm/utils/codegen-diff
+++ b/llvm/utils/codegen-diff
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 use Getopt::Std;
 $DEBUG = 0;
diff --git a/llvm/utils/findsym.pl b/llvm/utils/findsym.pl
--- a/llvm/utils/findsym.pl
+++ b/llvm/utils/findsym.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl -w
+#!/usr/bin/env perl
 #
 # Program:  findsym.pl
 #
@@ -8,6 +8,8 @@
 # Syntax:   findsym.pl <directory_with_libraries_in_it> <symbol>
 #
 
+use warnings;
+
 # Give first option a name.
 my $Directory = $ARGV[0];
 my $Symbol = $ARGV[1];
diff --git a/llvm/utils/llvm-compilers-check b/llvm/utils/llvm-compilers-check
--- a/llvm/utils/llvm-compilers-check
+++ b/llvm/utils/llvm-compilers-check
@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 ##===- utils/llvmbuild - Build the LLVM project ----------------*-python-*-===##
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
diff --git a/llvm/utils/llvm-native-gxx b/llvm/utils/llvm-native-gxx
--- a/llvm/utils/llvm-native-gxx
+++ b/llvm/utils/llvm-native-gxx
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 # Wrapper around LLVM tools to generate a native .o from llvm-gxx using an
 # LLVM back-end (CBE by default).
 
diff --git a/openmp/runtime/tools/check-execstack.pl b/openmp/runtime/tools/check-execstack.pl
--- a/openmp/runtime/tools/check-execstack.pl
+++ b/openmp/runtime/tools/check-execstack.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 #
 #//===----------------------------------------------------------------------===//
diff --git a/openmp/runtime/tools/check-instruction-set.pl b/openmp/runtime/tools/check-instruction-set.pl
--- a/openmp/runtime/tools/check-instruction-set.pl
+++ b/openmp/runtime/tools/check-instruction-set.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 #
 #//===----------------------------------------------------------------------===//
diff --git a/openmp/runtime/tools/message-converter.pl b/openmp/runtime/tools/message-converter.pl
--- a/openmp/runtime/tools/message-converter.pl
+++ b/openmp/runtime/tools/message-converter.pl
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 #
 #//===----------------------------------------------------------------------===//
diff --git a/polly/lib/External/isl/doc/mypod2latex b/polly/lib/External/isl/doc/mypod2latex
--- a/polly/lib/External/isl/doc/mypod2latex
+++ b/polly/lib/External/isl/doc/mypod2latex
@@ -1,4 +1,4 @@
-#!/usr/bin/perl
+#!/usr/bin/env perl
 
 use strict;
 use Pod::LaTeX;