Install Win32::Socketpair and do:

#! perl -slw
use strict;
use Win32::Socketpair qw[ winopen2 ];

## Run the command and get a bi-direction pipe to it.
my $pipe = winopen2( 'RunMe.exe arg arg arg' );

## Fetch the results from the pipe
my @results = <$pipe>;

## Send enter to it
print $pipe "\n";

## use @results here
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Not working. It keeps on waiting for pipe to close.

Then you are using it wrong!

Using the perl script as a substitute for your runme.exe:

#! perl -slw
use strict;

printf "%030d\n", $_ for 1 .. 1e3;
print "Press enter to exit";
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And this Perl script to run the above using winopen2():

#! perl -slw
use strict;
use Win32::Socketpair qw[ winopen2 ];

## Run the command and get a bi-direction pipe to it.
my $pipe = winopen2( 'RunMe.pl' );
my @results = <$pipe>;
print $pipe "\n";

print scalar @results;

<STDIN>;
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The latter reads a thousand lines from the former, sends "\n" to it which allows it to end, and then prints out the number of lines read (1001 including the "Press Enter to exit prompt") amd waits. If you check the task manager you'll see that the child process has terminated:

[12:05:50.87] C:\test>winopen2-test.pl
1001


[12:06:00.23] C:\test>
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---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

The start of some sanity?

You can open a pipe to the program (see perlopentut), and print a newline to the pipe. With a bit of luck, that has the same effect than pressing Enter.

Aren't backticks blocking?

Please make sure that the program has no keyword which runs it in a non interactive mode, such as /q. If it does not, perhaps a note to the developer to suggest that it should have?