You're getting ENOTTY from the system. The error may be yours, or the ISP's httpd may be misconfigured, but nobody can guess which until we see your code. Look for a statement printing or warning or die-ing with arguments ('Who are you?: ', $!).

They're most likely calling something else (via system or some variant of qx//) which expects to be run from a tty. Given the particular error message passwd would be my guess presuming some flavour of Linux.

And given that they don't know enough about *NIX to know that passwd is going to try to read from its TTY rather than stdin they probably don't want to be writing a web sysadmin interface . . .

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I shouldn't have said nobody can guess; yours sounds very likely. OP should not try to set up system accounts for http authentication.

++Fletch for nailing what was bothering me about the question.

After Compline,
Zaxo