Thank you! That is! It works perfectly, provided the "-" is used. I just correct it here for future reference.

my $cmd = qq(files\\pdftotext "$path_folder/$TextID" - |);
my $pid = open (FILE, $cmd)
    or die "Couldn't spawn [$cmd]: $! / $?";
$text = do { local($/); <FILE> };
close FILE;
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