I think you are looking for select or probably more conveniently IO::Select or even POE::Loop::Select.

/J\

I'm not sure what I want to do could be done with any of those...

As an example, suppose I had STDOUT, wanted to keep it that way (as an output channel) but also wanted to print everything that went to STDOUT to two other files... with one single print.

I can't see how to do this with IO::Select...

Perhaps IO::Tee is what you're looking for...

thor

Feel the white light, the light within
Be your own disciple, fan the sparks of will
For all of us waiting, your kingdom will come

You can tie the filehandle to a class that adds any amount of behind-the-scenes functionality to the basic filehandle. To the rest of your script, the filehandle would look and behave pretty much like a regular filehandle, but behind the scenes all sorts of stuff can be going on. perltie has info on how to do this, and you can also read more at Tie::Handle.

This sort of approach isn't for the faint of heart, so be sure to get yourself in good physical and mental shape before trying these stunts. *wink*

#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = new MainWindow;

my $t = $mw->Text(-width => 80, -height => 25, -wrap => 'none')->pack(
+-expand => 1);

open(CHILD, "./some_program 2>&1 |") 
                 or die "Can't open: $!";

$mw->fileevent(\*CHILD, 'readable',
                [\&fill_text_widget,$t]);
MainLoop;

sub fill_text_widget {
          my($widget) = @_;

          $_ = <CHILD>;

          $widget->insert('end', $_);
          $widget->yview('end');

}
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