Ok well I just ran into this post, and I think that the conversation got muddled... the Key is if you're doing a bidirectional pipe to close the Writer stream... Sorry about updating an old post, but its first Google response.

sub pushusers() {
    my $host = shift;
    my $cmd = sprintf("ssh %s@%s perl",$user,$host);
    my $pid = open2(*Reader, *Writer, $cmd);

    print Writer "die('got into perl')\n";
    close(Writer);
    my $output = <Reader>;
    print "Got from host ${host} output: ${output}";
    exit(0);
}
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-Anacreo