Ok, I think I've solved it. I won't even start on how annoying this is, and how much I wish I'd figured it out sooner. I'm still a little mystified on why it's failing in the original code, though. I have a theory, but I don't know Perl internals well enough to know if it's correct.

Basically, it's the part where I grab the filehandle via shift that is blowing up the program. It seems to be tightly associating my lexical loop variable with the filehandle, and then when the variable (and thus the filehandle) go out of scope at the end of the loop, it's trying to cleanup the filehandle (by closeing and waiting on it.

my $fd = shift @{$_};
my $child = shift @{$_};

[download]

When I replace that with the following:

my $fd = $_->[0];
my $child = $_->[1];

[download]

It works.

My theory is that because the underlying container where the filehandle is being stored is an array reference, that when I shift on the (dereferenced) array reference, I'm stomping on the original, even though it's in a for loop and using $_.

Does that sound right? Chalk it up to the care needed for references and reference "copies", I suppose.

In reply to Re: Select on child output problem by topher
in thread Select on child output problem by topher

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.