There is no Perl function whose second argument is in scalar context.

Heh, I'd've bet money that this claim is overstated. And I didn't have to scroll down very far (in the list in opcode.pl) before finding my first counterexample, bless. This is quickly followed by a long list of exceptions that are all binary operators so I'll let those go. Then we have atan2, substr, vec, index, rindex, crypt, unpack, split, splice, open, binmode, tie, dbmopen, select, read, sysopen, sysseek, sysread, syswrite, send, recv, seek, truncate, fcntl, ioctl, socket, socketpair, bind, connect, listen, accept, shutdown, getsockopt, setsockopt, rename, link, symlink, mkdir, opendir, seekdir, waitpid, setpgrp, getpriority, setpriority, shmget, shmctl, shmread, shmwrite, msgget, msgctl, msgsnd, msgrcv, semget, semctl, semop, gethostbyaddr, getnetbyaddr, getservbyname, and getservbyport.

So I really think I have to disagree with your claim. (: