I am seeing an issue with perl v5.20.2 exiting unexpectedly, and I don't know how to track down the source of the problem. Here's the code I'm trying to run:

use strict;
use warnings;
use Sys::Cmd 'spawn';

my $proc = spawn( 'file-not-found' } );
$proc->stdin->print("x\n");
$proc->wait_child;
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Note that Sys::Cmd (my own module) fiddles around a lot with file descriptors (and that is most likely the actual issue). But the problem I have at the moment is that the perl process appears to be terminating on the print statement:

main::(j:5):    my $proc = spawn( sub { print "hello\n" } );
  DB<1> n
main::(j:6):    warn ref $proc->stdin;
  DB<1> n
IO::Handle at j line 6.
 at j line 6.
main::(j:7):    $proc->stdin->print("x\n");
  DB<1> n
mark@mlt:~/src/sys-cmd$
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If I change the print statement to print {$proc->stdin} "text\n" the it appears as if perl tries to run the statement twice!

main::(j:5):    my $proc = spawn( sub { print "hello\n" } );
  DB<1> n
main::(j:6):    warn ref $proc->stdin;
  DB<1> n
IO::Handle at j line 6.
 at j line 6.
main::(j:7):    print {$proc->stdin} "x\n";
  DB<1> n
main::(j:7):    print {$proc->stdin} "x\n";
  DB<1> n
mark@mlt:~/src/sys-cmd$
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Without an error message I don't even know how to debug my actual issue. Any ideas?

p.s. I'm actually running a patched version of Sys::Cmd locally so you won't be able to re-create this without modification.

Update: I've created a new branch on github that you can check out to see what I'm trying to do:

$ git clone -b unexpected-termination  git://github.com/mlawren/sys-cm
+d
$ cd sys-cmd
$ ./unexpected-termination.pl
Spawning process
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Update 2: I just checked and no END block is run, and the exit value after termination is 141, which means nothing to me.

Update 3: The above errors were seen on Debian GNU/Linux. I *don't* see this behaviour with Perl 5.18.3 on Win32, where the test script runs to completion with normal error reporting.