If this approach works, it should be possible. See the documentation for open, or IO::Scalar/IO::String

Yes it works. Would it be correct to do it through | this way:

my $stdin_str = "";
read (STDIN, $stdin_str, $ENV{'CONTENT_LENGTH'});

open FH, ">|" or die $!;
print FH $stdin_str;

open STDIN, "<|" or die $!;

my $q = new CGI;

close STDIN;
close FH;
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Try it. I rarely use |, but it doesn't look like it would work to me , which is why I recommended opening to a scalar