ファイルハンドルを途中で読み込み止めるにはどうするのがいいのかな。。。

gistfile1.pl

use strict;
use warnings;
use IO::Handle;

my ($parent_in, $parent_out);
my ($child_in, $child_out);

pipe $parent_out, $child_in;
pipe $child_out, $parent_in;

$parent_in->autoflush(1);
$child_in->autoflush(1);

if (my $pid = fork) {
    close $parent_in; close $parent_out;

    print $child_in 'select @@version;'."\n";
    while (my $line = <$child_out>) {
        print $line;
    }
    # waiting...
    # not execute below..
    print $child_in 'show databases;'."\n";
    while (my $line = <$child_out>) {
        print $line;
    }

    close $child_in;
    close $child_out;
    waitpid($pid,0);
} else {
    die "cannot fork: $!" unless defined $pid;
    close $child_in; close $child_out;

    open STDOUT, '>&', $parent_in;
    open STDIN, '<&', $parent_out;

    exec "mysql -n -uroot" or exit;
}