Not clear about your actual situation, but the following code does prove that child processes being forked would be aware of the files opened by parents. But when to close is a little bit tricky, the sync stuff.

use strict;

my $file;
open($file, ">abc");
my $ret = fork;
if ($ret) {
    print $file "log from parent\n";
    sleep(5);
    close($file);
} else {
    print $file "log from child\n";
}
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