Setting Up Perl on Windows

Make

You need a "make" program to build the sources. If you are using Visual C++ or the Windows SDK tools, you can use nmake supplied with Visual C++ or Windows SDK. You may also use gmake instead of nmake. Builds using gcc need gmake. nmake is not supported for gcc builds. Parallel building is only supported with gmake, not nmake.

Command Shell

Use the default "cmd" shell that comes with Windows. Some versions of the popular 4DOS/NT shell have incompatibilities that may cause you trouble. If the build fails under that shell, try building again with the cmd shell.

Make sure the path to the build directory does not contain spaces. The build usually works in this circumstance, but some tests will fail.

Microsoft Visual C++

The nmake that comes with Visual C++ will suffice for building. Visual C++ requires that certain things be set up in the console before Visual C++ will successfully run. To make a console box be able to run the C compiler, you will need to beforehand, run "vcvarsall.bat x86" to compile for x86-32 and for x86-64 "vcvarsall.bat amd64". On a typical install of a Microsoft C++ compiler product, these batch files will already be in your "PATH" environment variable so you may just type them without an absolute path into your console. If you need to find the absolute path to the batch file, it is usually found somewhere like C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC. With some newer Microsoft C products (released after ~2004), the installer will put a shortcut in the start menu to launch a new console window with the console already set up for your target architecture (x86-32 or x86-64 or IA64). With the newer compilers, you may also use the older batch files if you choose so.

Microsoft Visual C++ 2008-2022 Express/Community Edition

These free versions of Visual C++ 2008-2022 Professional contain the same compilers and linkers that ship with the full versions, and also contain everything necessary to build Perl, rather than requiring a separate download of the Windows SDK like previous versions did.

These packages can be downloaded by searching in the Download Center at <https://www.microsoft.com/downloads/search.aspx?displaylang=en>. (Providing exact links to these packages has proven a pointless task because the links keep on changing so often.)

Install Visual C++ 2008-2022 Express/Community, then setup your environment using, e.g.

 C:\Program Files\Microsoft Visual Studio 12.0\Common7\Tools\vsvars32.bat
    

(assuming the default installation location was chosen).

Perl should now build using the win32/Makefile. You will need to edit that file to set CCTYPE to one of MSVC90-MSVC142 first.

Microsoft Visual C++ 2005 Express Edition

This free version of Visual C++ 2005 Professional contains the same compiler and linker that ship with the full version, but doesn't contain everything necessary to build Perl.

You will also need to download the "Windows SDK" (the "Core SDK" and "MDAC SDK" components are required) for more header files and libraries.

These packages can both be downloaded by searching in the Download Center at <http://www.microsoft.com/downloads/search.aspx?displaylang=en>. (Providing exact links to these packages has proven a pointless task because the links keep on changing so often.)

Try to obtain the latest version of the Windows SDK. Sometimes these packages contain a particular Windows OS version in their name, but actually work on other OS versions too. For example, the "Windows Server 2003 R2 Platform SDK" also runs on Windows XP SP2 and Windows 2000.

Install Visual C++ 2005 first, then the Platform SDK. Setup your environment as follows (assuming default installation locations were chosen):

 SET PlatformSDKDir=C:\Program Files\Microsoft Platform SDK

 SET PATH=%SystemRoot%\system32;%SystemRoot%;C:\Program Files\Microsoft Visual Studio 8\Common7\IDE;C:\Program Files\Microsoft Visual Studio 8\VC\BIN;C:\Program Files\Microsoft Visual Studio 8\Common7\Tools;C:\Program Files\Microsoft Visual Studio 8\SDK\v2.0\bin;C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727;C:\Program Files\Microsoft Visual Studio 8\VC\VCPackages;%PlatformSDKDir%\Bin

 SET INCLUDE=C:\Program Files\Microsoft Visual Studio 8\VC\INCLUDE;%PlatformSDKDir%\include

 SET LIB=C:\Program Files\Microsoft Visual Studio 8\VC\LIB;C:\Program Files\Microsoft Visual Studio 8\SDK\v2.0\lib;%PlatformSDKDir%\lib

 SET LIBPATH=C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727
    

(The PlatformSDKDir might need to be set differently depending on which version you are using. Earlier versions installed into "C:\Program Files\Microsoft SDK", while the latest versions install into version-specific locations such as "C:\Program Files\Microsoft Platform SDK for Windows Server 2003 R2".)

Perl should now build using the win32/Makefile. You will need to edit that file to set

 CCTYPE = MSVC80
    

and to set CCHOME, CCINCDIR and CCLIBDIR as per the environment setup above.

Microsoft Visual C++ Toolkit 2003

This free toolkit contains the same compiler and linker that ship with Visual C++ .NET 2003 Professional, but doesn't contain everything necessary to build Perl.

You will also need to download the "Platform SDK" (the "Core SDK" and "MDAC SDK" components are required) for header files, libraries and rc.exe, and ".NET Framework SDK" for more libraries and nmake.exe. Note that the latter (which also includes the free compiler and linker) requires the ".NET Framework Redistributable" to be installed first. This can be downloaded and installed separately, but is included in the "Visual C++ Toolkit 2003" anyway.

These packages can all be downloaded by searching in the Download Center at <https://www.microsoft.com/downloads/search.aspx?displaylang=en>. (Providing exact links to these packages has proven a pointless task because the links keep on changing so often.)

Try to obtain the latest version of the Windows SDK. Sometimes these packages contain a particular Windows OS version in their name, but actually work on other OS versions too. For example, the "Windows Server 2003 R2 Platform SDK" also runs on Windows XP SP2 and Windows 2000.

Install the Toolkit first, then the Platform SDK, then the .NET Framework SDK. Setup your environment as follows (assuming default installation locations were chosen):

 SET PlatformSDKDir=C:\Program Files\Microsoft Platform SDK

 SET PATH=%SystemRoot%\system32;%SystemRoot%;C:\Program Files\Microsoft Visual C++ Toolkit 2003\bin;%PlatformSDKDir%\Bin;C:\Program Files\Microsoft.NET\SDK\v1.1\Bin

 SET INCLUDE=C:\Program Files\Microsoft Visual C++ Toolkit 2003\include;%PlatformSDKDir%\include;C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\include

 SET LIB=C:\Program Files\Microsoft Visual C++ Toolkit 2003\lib;%PlatformSDKDir%\lib;C:\Program Files\Microsoft Visual Studio .NET 2003\Vc7\lib
    

(The PlatformSDKDir might need to be set differently depending on which version you are using. Earlier versions installed into "C:\Program Files\Microsoft SDK", while the latest versions install into version-specific locations such as "C:\Program Files\Microsoft Platform SDK for Windows Server 2003 R2".)

Several required files will still be missing:

        CCTYPE = MSVC70FREE

Microsoft Platform SDK 64-bit Compiler

The nmake that comes with the Platform SDK will suffice for building Perl. Make sure you are building within one of the "Build Environment" shells available after you install the Platform SDK from the Start Menu.

GCC

Perl can be compiled with gcc from MinGW (version 3.4.5 or later) or from MinGW64 (version 4.4.3 or later). It can be downloaded here:

<http://www.mingw.org/> <http://www.mingw-w64.org/>

You also need gmake. Usually it comes with MinGW but its executable may have a different name, such as mingw32-make.exe.

Note that the MinGW build currently fails with version 6.3.0 or later.

Note also that the C++ mode build currently fails with MinGW 3.4.5 and 4.7.2 or later, and with MinGW64 64-bit 6.3.0 or later.

Intel C++ Compiler

Experimental support for using Intel C++ Compiler has been added. Edit win32/Makefile and pick the correct CCTYPE for the Visual C that Intel C was installed into. Also uncomment __ICC to enable Intel C on Visual C support. To set up the build environment, from the Start Menu run IA-32 Visual Studio 20__ mode or Intel 64 Visual Studio 20__ mode as appropriate. Then run nmake as usually in that prompt box.

Only Intel C++ Compiler v12.1 has been tested. Other versions probably will work. Using Intel C++ Compiler instead of Visual C has the benefit of C99 compatibility which is needed by some CPAN XS modules, while maintaining compatibility with Visual C object code and Visual C debugging infrastructure unlike GCC.

Building

• Make sure you are in the "win32" subdirectory under the perl toplevel. This directory contains a "Makefile" that will work with versions of nmake that come with Visual C++ or the Windows SDK, and a GNU make "GNUmakefile" that will work for all supported compilers. The defaults in the gmake makefile are setup to build using MinGW/gcc.
• Edit the GNUmakefile (or Makefile, if you're using nmake) and change the values of INST_DRV and INST_TOP. You can also enable various build flags. These are explained in the makefiles.

  Note that it is generally not a good idea to try to build a perl with INST_DRV and INST_TOP set to a path that already exists from a previous build. In particular, this may cause problems with the lib/ExtUtils/t/Embed.t test, which attempts to build a test program and may end up building against the installed perl's lib/CORE directory rather than the one being tested.

  You will have to make sure that CCTYPE is set correctly and that CCHOME points to wherever you installed your compiler. For GCC this should be the directory that contains the bin, include and lib directories.

  If building with the cross-compiler provided by mingw-w64.org you'll need to uncomment the line that sets GCCCROSS in the GNUmakefile. Do this only if it's the cross-compiler - ie only if the bin folder doesn't contain a gcc.exe. (The cross-compiler does not provide a gcc.exe, g++.exe, ar.exe, etc. Instead, all of these executables are prefixed with 'x86_64-w64-mingw32-'.)

  The default value for CCHOME in the makefiles for Visual C++ may not be correct for some versions. Make sure the default exists and is valid.

  If you want build some core extensions statically into perl's dll, specify them in the STATIC_EXT macro.

  Be sure to read the instructions near the top of the makefiles carefully.

• Type "gmake" (or "nmake" if you are using that make).

  This should build everything. Specifically, it will create perl.exe, perl534.dll at the perl toplevel, and various other extension dll's under the lib\auto directory. If the build fails for any reason, make sure you have done the previous steps correctly.

  To try gmake's parallel mode, type "gmake -j2", where 2, is the maximum number of parallel jobs you want to run. A number of things in the build process will run in parallel, but there are serialization points where you will see just 1 CPU maxed out. This is normal.

  If you are advanced enough with building C code, here is a suggestion to speed up building perl, and the later "make test". Try to keep your PATH environmental variable with the least number of folders possible (remember to keep your C compiler's folders there). "C:\WINDOWS\system32" or "C:\WINNT\system32" depending on your OS version should be first folder in PATH, since "cmd.exe" is the most commonly launched program during the build and later testing.

Testing Perl on Windows

There should be no test failures.

If you build with Visual C++ 2013 then three tests currently may fail with Daylight Saving Time related problems: t/io/fs.t, cpan/HTTP-Tiny/t/110_mirror.t and lib/File/Copy.t. The failures are caused by bugs in the CRT in VC++ 2013 which are fixed in VC++2015 and later, as explained by Microsoft here: <https://connect.microsoft.com/VisualStudio/feedback/details/811534/utime-sometimes-fails-to-set-the-correct-file-times-in-visual-c-2013>. In the meantime, if you need fixed "stat" and "utime" functions then have a look at the CPAN distribution Win32::UTCFileTime.

If you build with Visual C++ 2015 or later then ext/XS-APItest/t/locale.t may crash (after all its tests have passed). This is due to a regression in the Universal CRT introduced in the Windows 10 April 2018 Update, and will be fixed in the May 2019 Update, as explained here: <https://developercommunity.visualstudio.com/content/problem/519486/setlocalelc-numeric-iso-latin-16-fails-then-succee.html>.

If you build with certain versions (e.g. 4.8.1) of gcc from www.mingw.org then ext/POSIX/t/time.t may fail test 17 due to a known bug in those gcc builds: see <https://sourceforge.net/p/mingw/bugs/2152/>.

Some test failures may occur if you use a command shell other than the native "cmd.exe", or if you are building from a path that contains spaces. So don't do that.

If you are running the tests from a emacs shell window, you may see failures in op/stat.t. Run "gmake test-notty" in that case.

Furthermore, you should make sure that during "make test" you do not have any GNU tool packages in your path: some toolkits like Unixutils include some tools ("type" for instance) which override the Windows ones and makes tests fail. Remove them from your path while testing to avoid these errors.

To see the output of specific failing tests run the harness from the t directory:

  # assuming you're starting from the win32 directory
  cd ..\win32
  .\perl harness <list of tests>

Please report any other failures as described under "BUGS AND CAVEATS".

Installation of Perl on Windows

To use the Perl you just installed you will need to add a new entry to your PATH environment variable: "$INST_TOP\bin", e.g.

    set PATH=c:\perl\bin;%PATH%

If you opted to uncomment "INST_VER" and "INST_ARCH" in the makefile then the installation structure is a little more complicated and you will need to add two new PATH components instead: "$INST_TOP\$INST_VER\bin" and "$INST_TOP\$INST_VER\bin\$ARCHNAME", e.g.

    set PATH=c:\perl\5.6.0\bin;c:\perl\5.6.0\bin\MSWin32-x86;%PATH%

Usage Hints for Perl on Windows

Environment Variables

The installation paths that you set during the build get compiled into perl, so you don't have to do anything additional to start using that perl (except add its location to your PATH variable).

If you put extensions in unusual places, you can set PERL5LIB to a list of paths separated by semicolons where you want perl to look for libraries. Look for descriptions of other environment variables you can set in perlrun.

You can also control the shell that perl uses to run system() and backtick commands via PERL5SHELL. See perlrun.

Perl does not depend on the registry, but it can look up certain default values if you choose to put them there unless disabled at build time with USE_NO_REGISTRY. On Perl process start Perl checks if "HKEY_CURRENT_USER\Software\Perl" and "HKEY_LOCAL_MACHINE\Software\Perl" exist. If the keys exists, they will be checked for remainder of the Perl process's run life for certain entries. Entries in "HKEY_CURRENT_USER\Software\Perl" override entries in "HKEY_LOCAL_MACHINE\Software\Perl". One or more of the following entries (of type REG_SZ or REG_EXPAND_SZ) may be set in the keys:

 lib-$]        version-specific standard library path to add to @INC
 lib           standard library path to add to @INC
 sitelib-$]    version-specific site library path to add to @INC
 sitelib       site library path to add to @INC
 vendorlib-$]  version-specific vendor library path to add to @INC
 vendorlib     vendor library path to add to @INC
 PERL*         fallback for all %ENV lookups that begin with "PERL"
    

Note the $] in the above is not literal. Substitute whatever version of perl you want to honor that entry, e.g. 5.6.0. Paths must be separated with semicolons, as usual on Windows.

File Globbing

By default, perl handles file globbing using the File::Glob extension, which provides portable globbing.

If you want perl to use globbing that emulates the quirks of DOS filename conventions, you might want to consider using File::DosGlob to override the internal glob() implementation. See File::DosGlob for details.

Using perl from the command line

If you are accustomed to using perl from various command-line shells found in UNIX environments, you will be less than pleased with what Windows offers by way of a command shell.

The crucial thing to understand about the Windows environment is that the command line you type in is processed twice before Perl sees it. First, your command shell (usually CMD.EXE) preprocesses the command line, to handle redirection, environment variable expansion, and location of the executable to run. Then, the perl executable splits the remaining command line into individual arguments, using the C runtime library upon which Perl was built.

It is particularly important to note that neither the shell nor the C runtime do any wildcard expansions of command-line arguments (so wildcards need not be quoted). Also, the quoting behaviours of the shell and the C runtime are rudimentary at best (and may, if you are using a non-standard shell, be inconsistent). The only (useful) quote character is the double quote ("). It can be used to protect spaces and other special characters in arguments.

The Windows documentation describes the shell parsing rules here: <https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/cmd> and the C runtime parsing rules here: <https://msdn.microsoft.com/en-us/library/17w5ykft%28v=VS.100%29.aspx>.

Here are some further observations based on experiments: The C runtime breaks arguments at spaces and passes them to programs in argc/argv. Double quotes can be used to prevent arguments with spaces in them from being split up. You can put a double quote in an argument by escaping it with a backslash and enclosing the whole argument within double quotes. The backslash and the pair of double quotes surrounding the argument will be stripped by the C runtime.

The file redirection characters "<", ">", and "|" can be quoted by double quotes (although there are suggestions that this may not always be true). Single quotes are not treated as quotes by the shell or the C runtime, they don't get stripped by the shell (just to make this type of quoting completely useless). The caret "^" has also been observed to behave as a quoting character, but this appears to be a shell feature, and the caret is not stripped from the command line, so Perl still sees it (and the C runtime phase does not treat the caret as a quote character).

Here are some examples of usage of the "cmd" shell:

This prints two doublequotes:

    perl -e "print '\"\"' "
    

This does the same:

    perl -e "print \"\\\"\\\"\" "
    

This prints "bar" and writes "foo" to the file "blurch":

    perl -e "print 'foo'; print STDERR 'bar'" > blurch
    

This prints "foo" ("bar" disappears into nowhereland):

    perl -e "print 'foo'; print STDERR 'bar'" 2> nul
    

This prints "bar" and writes "foo" into the file "blurch":

    perl -e "print 'foo'; print STDERR 'bar'" 1> blurch
    

This pipes "foo" to the "less" pager and prints "bar" on the console:

    perl -e "print 'foo'; print STDERR 'bar'" | less
    

This pipes "foo\nbar\n" to the less pager:

    perl -le "print 'foo'; print STDERR 'bar'" 2>&1 | less
    

This pipes "foo" to the pager and writes "bar" in the file "blurch":

    perl -e "print 'foo'; print STDERR 'bar'" 2> blurch | less
    

Discovering the usefulness of the "command.com" shell on Windows 9x is left as an exercise to the reader :)

One particularly pernicious problem with the 4NT command shell for Windows is that it (nearly) always treats a % character as indicating that environment variable expansion is needed. Under this shell, it is therefore important to always double any % characters which you want Perl to see (for example, for hash variables), even when they are quoted.

Building Extensions

The Comprehensive Perl Archive Network (CPAN) offers a wealth of extensions, some of which require a C compiler to build. Look in <https://www.cpan.org/> for more information on CPAN.

Note that not all of the extensions available from CPAN may work in the Windows environment; you should check the information at <https://www.cpantesters.org/> before investing too much effort into porting modules that don't readily build.

Most extensions (whether they require a C compiler or not) can be built, tested and installed with the standard mantra:

    perl Makefile.PL
    $MAKE
    $MAKE test
    $MAKE install
    

where $MAKE is whatever 'make' program you have configured perl to use. Use "perl -V:make" to find out what this is. Some extensions may not provide a testsuite (so "$MAKE test" may not do anything or fail), but most serious ones do.

It is important that you use a supported 'make' program, and ensure Config.pm knows about it.

Note that MakeMaker actually emits makefiles with different syntax depending on what 'make' it thinks you are using. Therefore, it is important that one of the following values appears in Config.pm:

    make='nmake'        # MakeMaker emits nmake syntax
    any other value     # MakeMaker emits generic make syntax
                            (e.g GNU make, or Perl make)
    

If the value doesn't match the 'make' program you want to use, edit Config.pm to fix it.

If a module implements XSUBs, you will need one of the supported C compilers. You must make sure you have set up the environment for the compiler for command-line compilation before running "perl Makefile.PL" or any invocation of make.

If a module does not build for some reason, look carefully for why it failed, and report problems to the module author. If it looks like the extension building support is at fault, report that with full details of how the build failed using the GitHub issue tracker at <https://github.com/Perl/perl5/issues>.

Command-line Wildcard Expansion

The default command shells on DOS descendant operating systems (such as they are) usually do not expand wildcard arguments supplied to programs. They consider it the application's job to handle that. This is commonly achieved by linking the application (in our case, perl) with startup code that the C runtime libraries usually provide. However, doing that results in incompatible perl versions (since the behavior of the argv expansion code differs depending on the compiler, and it is even buggy on some compilers). Besides, it may be a source of frustration if you use such a perl binary with an alternate shell that *does* expand wildcards.

Instead, the following solution works rather well. The nice things about it are 1) you can start using it right away; 2) it is more powerful, because it will do the right thing with a pattern like */*/*.c; 3) you can decide whether you do/don't want to use it; and 4) you can extend the method to add any customizations (or even entirely different kinds of wildcard expansion).

 C:\> copy con c:\perl\lib\Wild.pm
 # Wild.pm - emulate shell @ARGV expansion on shells that don't
 use File::DosGlob;
 @ARGV = map {
              my @g = File::DosGlob::glob($_) if /[*?]/;
              @g ? @g : $_;
            } @ARGV;
 1;
 ^Z
 C:\> set PERL5OPT=-MWild
 C:\> perl -le "for (@ARGV) { print }" */*/perl*.c
 p4view/perl/perl.c
 p4view/perl/perlio.c
 p4view/perl/perly.c
 perl5.005/win32/perlglob.c
 perl5.005/win32/perllib.c
 perl5.005/win32/perlglob.c
 perl5.005/win32/perllib.c
 perl5.005/win32/perlglob.c
 perl5.005/win32/perllib.c
    

Note there are two distinct steps there: 1) You'll have to create Wild.pm and put it in your perl lib directory. 2) You'll need to set the PERL5OPT environment variable. If you want argv expansion to be the default, just set PERL5OPT in your default startup environment.

If you are using the Visual C compiler, you can get the C runtime's command line wildcard expansion built into perl binary. The resulting binary will always expand unquoted command lines, which may not be what you want if you use a shell that does that for you. The expansion done is also somewhat less powerful than the approach suggested above.

Notes on 64-bit Windows

Windows .NET Server supports the LLP64 data model on the Intel Itanium architecture.

The LLP64 data model is different from the LP64 data model that is the norm on 64-bit Unix platforms. In the former, "int" and "long" are both 32-bit data types, while pointers are 64 bits wide. In addition, there is a separate 64-bit wide integral type, "__int64". In contrast, the LP64 data model that is pervasive on Unix platforms provides "int" as the 32-bit type, while both the "long" type and pointers are of 64-bit precision. Note that both models provide for 64-bits of addressability.

64-bit Windows running on Itanium is capable of running 32-bit x86 binaries transparently. This means that you could use a 32-bit build of Perl on a 64-bit system. Given this, why would one want to build a 64-bit build of Perl? Here are some reasons why you would bother:

Running Perl Scripts

Instead, all available methods to execute plain text files on Windows rely on the file "extension". There are three methods to use this to execute perl scripts:

1.

There is a facility called "file extension associations". This can be manipulated via the two commands "assoc" and "ftype" that come standard with Windows. Type "ftype /?" for a complete example of how to set this up for perl scripts (Say what? You thought Windows wasn't perl-ready? :).

2.

Since file associations don't work everywhere, and there are reportedly bugs with file associations where it does work, the old method of wrapping the perl script to make it look like a regular batch file to the OS, may be used. The install process makes available the "pl2bat.bat" script which can be used to wrap perl scripts into batch files. For example:

        pl2bat foo.pl
    

will create the file "FOO.BAT". Note "pl2bat" strips any .pl suffix and adds a .bat suffix to the generated file.

If you use the 4DOS/NT or similar command shell, note that "pl2bat" uses the "%*" variable in the generated batch file to refer to all the command line arguments, so you may need to make sure that construct works in batch files. As of this writing, 4DOS/NT users will need a "ParameterChar = *" statement in their 4NT.INI file or will need to execute "setdos /p*" in the 4DOS/NT startup file to enable this to work.

3.

Using "pl2bat" has a few problems: the file name gets changed, so scripts that rely on $0 to find what they must do may not run properly; running "pl2bat" replicates the contents of the original script, and so this process can be maintenance intensive if the originals get updated often. A different approach that avoids both problems is possible.

A script called "runperl.bat" is available that can be copied to any filename (along with the .bat suffix). For example, if you call it "foo.bat", it will run the file "foo" when it is executed. Since you can run batch files on Windows platforms simply by typing the name (without the extension), this effectively runs the file "foo", when you type either "foo" or "foo.bat". With this method, "foo.bat" can even be in a different location than the file "foo", as long as "foo" is available somewhere on the PATH. If your scripts are on a filesystem that allows symbolic links, you can even avoid copying "runperl.bat".

Here's a diversion: copy "runperl.bat" to "runperl", and type "runperl". Explain the observed behavior, or lack thereof. :) Hint: .gnidnats llits er'uoy fi ,"lrepnur" eteled :tniH

Miscellaneous Things

"perldoc" is also a useful tool for browsing information contained in the documentation, especially in conjunction with a pager like "less" (recent versions of which have Windows support). You may have to set the PAGER environment variable to use a specific pager. "perldoc -f foo" will print information about the perl operator "foo".

One common mistake when using this port with a GUI library like "Tk" is assuming that Perl's normal behavior of opening a command-line window will go away. This isn't the case. If you want to start a copy of "perl" without opening a command-line window, use the "wperl" executable built during the installation process. Usage is exactly the same as normal "perl" on Windows, except that options like "-h" don't work (since they need a command-line window to print to).

If you find bugs in perl, you can report them to <https://github.com/Perl/perl5/issues>.