MSYS2's perl -p detect STDIN as pipe wrongly. It works in MSYS-1.0 (with mintty).

[johnnytemp]

Run this in MSYS2 (mintty shell):

perl -e 'print("pipe!") if (-p STDIN)'

Output:

pipe!

Expect to output nothing. STDIN is not a pipe if not piped.

This can break many perl programs... like "ack -f" command -> "ack: No regular expression found." (error)

[mati865]

If you use MSYS2 perl (MSYS2 shell) it outputs nothing:

MSYS ~
$ perl -e 'print("pipe!") if (-p STDIN)'

MSYS ~

[johnnytemp]

My perl is not specific to MSYS2 perl. It is a windows own installation. "which perl" -> path is C:\Perl\bin\perl.exe. My MSYS2 environment doesn't pre-installed perl.

My MSYS2 install file is msys2-i686-20161025.exe. I run MSYS2 from C:\msys32\msys2.exe. And perl version is (installation file ActivePerl-5.18.1.1800-MSWin32-x86-64int-297570.msi):

$ perl --version

This is perl 5, version 18, subversion 1 (v5.18.1) built for MSWin32-x86-multi-thread-64int
(with 1 registered patch, see perl -V for more detail)

Copyright 1987-2013, Larry Wall

Binary build 1800 [297570] provided by ActiveState http://www.ActiveState.com
Built Sep 20 2013 11:40:34

Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.

Complete documentation for Perl, including FAQ lists, should be found on
this system using "man perl" or "perldoc perl". If you have access to the
Internet, point your browser at http://www.perl.org/, the Perl Home Page.

Remark: MSYS-1.0 works with that Windows-native perl gracefully.