Your string $hostname still has the newline at the end of it, which is why the error message shows on two lines:

Invalid TLD found in '200-206-30-98.customer.tdatabrasil.net.br
' at b2.pl line 9.
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Remove all whitespace from the end of $hostname after you've read it from the file:

$hostname =~ s/\s+$//;
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That way, the call to public_suffix() should succeed.