Author image Kent Fredric (PAUSE Custodial Account)


IPC::Run::Fused - Capture Stdout/Stderr simultaneously as if it were one stream, painlessly.


version 1.000001


  use IPC::Run::Fused qw( run_fused );

  run_fused( my $fh, $stderror_filled_program, '--file', $tricky_filename, @moreargs ) || die "Argh $@";
  open my $fh, '>', 'somefile.txt' || die "NOO  $@";

  # Simple implementation of 'tee' like behaviour,
  # sending to stdout and to a file.

  while ( my $line = <$fh> ) {
    print $fh $line;
    print $line;


Have you ever tried to do essentially the same as you would in bash do to this:

  parentapp <( app 2>&1  )

And found massive road works getting in the way.

Sure, you can always do this style syntax:

  open my $fh, 'someapp --args foo 2>&1 |';

But that's not very nice, because

1. you're relying on a sub-shell to do that for you
2. you have to manually escape everything
3. you can't use list context.

And none of this is very Modern or Nice


This code is barely tested, its here, because I spent hours griping about how the existing ways suck.


1. No String Interpolation.

Arguments after the first work as if you'd passed them directly to 'system'. You can be as dangerous or as safe as you want with them. We recommend passing a list, but a string ( as a scalar reference ) should work

But if you're using a string, this modules probably not affording you much.

2. No dicking around with managing multiple file handles yourself.

I looked at IPC::Run, IPC::Run3 and IPC::Open3, and they all seemed very unfriendly, and none did what I wanted.

3. Non-global file-handles supported by design.

All the competition seem to still have this thing for global file handles and you having to use them. Yuck!.

We have a few global file-handles inside our code, but they're only STDERR and STDOUT, at present I don't think I can circumvent that. If I ever can, I'll endeavor to do so ☺


No functions are exported by default, be explicit with what you want.

At this time there is only one, and there are no plans for more.


  run_fused( $fh, $executable, @params ) || die "$@";
  run_fused( $fh, \$command_string )     || die "$@";
  run_fused( $fh, sub { .. } )           || die "$@";

  # Recommended

  run_fused( my $fh, $execuable, @params ) || die "$@";

  # Somewhat supported

  run_fused( my $fh, \$command_string ) || die "$@";

$fh will be clobbered like 'open' does, and $cmd, @args will be passed, as-is, through to exec() or system().

$fh will point to an IO::Handle attached to the end of a pipe running back to the called application.

the command will be run in a fork, and STDERR and STDOUT "fused" into a singular pipe.

NOTE: at present, STDIN's file-descriptor is left unchanged, and child processes will inherit parent STDIN's, and will thus block ( somewhere ) waiting for response.


Kent Fredric <>


This software is copyright (c) 2017 by Kent Fredric <>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.