Hello everyone, I am looking for a way to open an external program, feed a set of data to it and capturing the output in a variable, much like using @var = `extprog blah blaha` - extprog returns a set of values each time it gets input.

The problem is that I have a lot of data (several million sets of coordinates) and it takes a bit of time to open and initialize the external program each time, hence I would like to open the external program once and feed the data through a pipe into the program, I was imagining something like this: (note that the code might have errors, just showing for illustration)
open EXT,"|extprog";
while (<>){
  @data = conv_data($_);
  print EXT "$data[0] $data[1]\n";
}
close EXT;

[download]

Now, my external program will get this data and put it's data on stdout. The question is how do I get hold of/redirect the output, preferrably without resorting to temporary files.

rgds,
Ole C.

Update
I got this sorted now, thanks for the replies. I also got a couple of requests to share my final code and what I ended up doing in the end, so I will post it here.
The output from my external program was buffered, so I could not use open3 as the read/write deadlocked. Hence I ended up using brother merlyns suggestion which at first seemed like pure magic but which made more sense after reading up on -|
My final code for achieving what I wanted then looked like this:
$run =
"mapproject -F --D_FORMAT=\%lf -I --ELLIPSOID=HELMERT1906  -Jt31/30/1:
+1 -R31/40/30/39 --MAP_SCALE_FACTOR=1.0000 ";
open FH, "<depths.asc.to" or die "could not open asc file\n";
if ( $pid = open RESULTS, "-|" ) {
    # I am the original process, so read from <RESULTS> below
}
else {
    # I am the kid
    if ( $pid1 = open STDIN, "-|" ) {
        # I am still the kid, but my STDIN is now piped from the grand
+kid
        exec "$run";
    }
    else {    # I am the grandkid: be a data pump
    while (<FH>) {    
        print "$_\n";
      }
        exit 0;
    }
}
while (<RESULTS>) {
    print $_;
}

[download]

In reply to output from an external program by olecs

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