You cut off a relevant part of the error message: "or string". You have a string literal (<<EOF .. EOF) which interpolates an undefined variable. $email_400, $main_domain, $ENV{REDIRECT_URL} or $ENV{HTTP_REFERER} evaluates to undef. A more recent version of Perl would actually identify which in the error message.

In reply to Re: uninitialized value in concatenation by ikegami
in thread uninitialized value in concatenation by Galceran

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