Where is the documentation for $# ?

Question

I can't seem to find explicit documentation for $# in perldoc.

Yes, I know what it is, and I can see implicit references in places like perllol and perldsc, but I can't seem to find anything standalone.

What's really surprising is that it doesn't have it's own section in perlvar.

Does such documentation exist? If so, where?

Answer 1

$# is not a special variable, it is a sigil like $, @, %, &, and *. Since it is just part of how arrays work, you will find it documented in perldoc perldata with the rest of the documentation on how variables work.

$#foo is just a way of asking @foo what its last index is. There is no separate symbol table entry for it (like there is for $foo, %foo, &foo, and the filehandle foo).

Answer 2

Actually, $# used to be a builtin variable:

$#

The output format for printed numbers. This variable is a half-hearted attempt to emulate awk's OFMT variable. There are times, however, when awk and perl have differing notions of what is in fact numeric. Also, the initial value is %.20g rather than %.6g, so you need to set $# explicitly to get awk's value. (Mnemonic: # is the number sign.)

$# was removed in 5.10.0.

See:

C:\> perl -e "print $#"
$# is no longer supported at -e line 1.

See also How do you google for -f>@+?*<.-&'_:$#/%!