Some code:

main.pl:
use strict;
use warnings;
use IO::Handle;
$^F = 100;

pipe READHANDLE,WRITEHANDLE;
binmode READHANDLE;
binmode WRITEHANDLE;
WRITEHANDLE->autoflush;
READHANDLE->autoflush;
unless (fork()){
        exec $^X, $ARGV[0], fileno(READHANDLE);
        die;
}
print WRITEHANDLE "Test!\n";
close WRITEHANDLE;
wait;

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subcommand1.pl:
open IN, "<&", $ARGV[0] or die $!;
binmode IN;
while(defined($_ = <IN>)) {
    print "line $_";
}
close IN;

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subcommand2.pl:
open IN, "<&", $ARGV[0] or die $!;
binmode IN;
my $s = <IN>;
print "line: $s";
close IN;

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Problem: 
perl main.pl subcommand1.pl

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hangs after first line, while 
perl main.pl subcommand2.pl

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works fine.
Also 
cat subcommand1.pl | perl subcommand1.pl 0

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works fine, meaning subcommand1.pl reads from file correctly.

So, I cannot understand why there is some kind of deadlock in subcommand1.pl?


UPD: SOLVED Re: File handle passing issue under *nix

In reply to [SOLVED] File handle passing issue under *nix by vsespb

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