in reply to 2 way pipe?

In addition to all of the above, have a look at IPC::Run. It's a very simple and intuitive interface for doing all the easy things, while at the same time being a pretty good interface for doing the hard things, too. For example: 
use IPC::Run qw( run );
# just a silly command to execute in another process, to demonstrate
# how input, output and error all relate
my $command = q<perl -lpe 's/b/t/; warn qq{Oh, no!  A z in "$_"!  What
+ a world, what a world!\n} if /z/'>;

# but that way is sensitive to what shell you are using,
# (whether it is ok to use ' or " to quote in the shell)
# this way is shell-independant:
$command = ['perl', '-lpe', 's/b/t/; warn qq{Oh, no!  A z in "$_"!  Wh
+at a world, what a world!\n} if /z/'];

my ($in, $out, $err);
$in = "foo\nbar\nbaz\n";
run $command, \$in, \$out, \$err;

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would give you "foo\ntar\ntaz\n"; in $out (the output of the program) and "Oh, no!  A z in "taz"!  What a world, what a world!\n" in $err (the STDERR of the program). 
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:Wq
Not an editor command: Wq

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