system_command_fail.txt

This is enough to flake. 
    try {
        my $cmd = System::Command->new( @cat, 'default' ) ;
        # binmode $cmd->stdout ;
        # $cmd->stdin->close ;
        # $cmd->stdout->read( my $buf, 100 ) ;
        # print "binary read of crlf encoded data \n" ;
        # fiducial_read( 'default', 'binary' ) ;
        # print "got     : ", hd( $buf ) ;
        print "\n" ;
        }
    catch { print "Locked\n" } ;

Warning: unable to close filehandle GEN11 properly: Bad file descriptor at C:/Strawberry/perl/vendor/lib/Try/Tiny.pm line 81.
Warning: unable to close filehandle GEN7 properly: Bad file descriptor at C:/Strawberry/perl/vendor/lib/Try/Tiny.pm line 81.
PS C:\Users\jacoby\Dropbox>

Trying this in Git Bash I get a bit more:

Warning: unable to close filehandle GEN11 properly: Bad file descriptor at c:/strawberry/perl/vendor/lib/Try/Tiny.pm line 81.
Warning: unable to close filehandle GEN7 properly: Bad file descriptor at c:/strawberry/perl/vendor/lib/Try/Tiny.pm line 81.

jacoby@GORT ~/Dropbox
$ Invalid argument opening STDIN as Win32 handle 388 in pumper 8344 at c:/strawberry/perl/vendor/lib/IPC/Run/Win32Pump.pm line 71.
Compilation failed in require.
BEGIN failed--compilation aborted.
Invalid argument opening STDIN as Win32 handle 408 in pumper 8388 at c:/strawberry/perl/vendor/lib/IPC/Run/Win32Pump.pm line 71.
Compilation failed in require.
BEGIN failed--compilation aborted.
Invalid argument opening STDIN as Win32 handle 412 in pumper 9320 at c:/strawberry/perl/vendor/lib/IPC/Run/Win32Pump.pm line 71.
Compilation failed in require.
BEGIN failed--compilation aborted.