See Re^3: How can I read DATA in parent and child? fdopen doesn't help, it's still the same shared seek pointer. *nix doesn't do what you want. If you want to do reads on handles, try this instead.

#!/usr/bin/perl

# https://perlmonks.org/?node_id=1230099

use strict;
use warnings;

open my $x, '<', \do { local $/; <DATA> };

my $who = fork() ? 'p' : 'c';

while( <$x> )
  {
  print "$who $_";
  }

1 while wait > 0;

__DATA__
a
b
c
d
e
[download]

Parent and child in my real world application need to have the same set of information to do different things with it.

Is this an XY Problem? The order of operations should then be:

1. Read and store all the data
2. Fork
3. Process all the already-read data in different ways