With IO::Select, this isn't too much to avoid, is it?
#!/usr/bin/perl
use diagnostics;
use strict 'subs';
use strict 'refs';
use Socket;
use IO::Handle;
use IO::Select; #### ADDED
my $child; #filehandle to child process
my $parent; #filehandle to parent process
my $pid; #Process ID of child process
socketpair($child, $parent, AF_UNIX, SOCK_STREAM, PF_UNSPEC)
or die "socketpair: $!
+";
$child->autoflush(1);
$parent->autoflush(1);
if ($pid = fork()) { #parent
close $parent or die "close: $!\n";
sleep 1;
print STDOUT time%1000, ": polling child\n";
if ( IO::Select->new($child)->can_read(0) ) { ############### CHA
+NGE
my $line = <$child>;
chomp $line;
print STDOUT time%1000, ": received <$line>\n";
} else {
print STDOUT time%1000, ": no input from child yet\n";
}
} else { #child
die "cannot fork: $!" unless defined $pid;
close $child or die "close: $!\n";
print STDOUT time%1000, ": child started\n";
sleep 5;
print {$parent} time%1000, ": child printed\n";
close $parent or die "close: $!\n";
exit;
}