Re: Perl allows package names consisting entirely of colons

[Athanasius]

in reply to Perl allows package names consisting entirely of colons

Seems to work only when the colons come in pairs:

#! perl
use strict;
use warnings;

package :::::
{
    sub x
    {
        printf "(%s)\n", __PACKAGE__;
    }
}

package main;

:::::::x();

Produces:

23:01 >perl 405_Obfu.pl
Bareword "::::::" refers to nonexistent package at 405_Obfu.pl line 27
+.
Invalid version format (non-numeric data) at 405_Obfu.pl line 17, near
+ "package ::::"
syntax error at 405_Obfu.pl line 17, near "package :::::"
Execution of 405_Obfu.pl aborted due to compilation errors.

23:02 >

“Curiouser and curiouser!” cried Alice.

Update: D’oh! (slaps forehead). Of course! :: is a synonym for main, and so is ::main and therefore ::::, likewise ::::::, etc., etc. (See Packages.) This “insight” is wrong — see reply by tobyink, below.

[tobyink]

In terms of the package keyword itself, :: and main are distinct packages, and :::: is another package entirely...

$ perl -Mstrict -Mwarnings -E'package main; say __PACKAGE__'
main
$ perl -Mstrict -Mwarnings -E'package ::main; say __PACKAGE__'
main
$ perl -Mstrict -Mwarnings -E'package ::; say __PACKAGE__'
::
$ perl -Mstrict -Mwarnings -E'package ::::; say __PACKAGE__'
::::

{
    package main;
    sub xxx { 0 };
    package ::;
    sub xxx { 1 };
    package ::::;
    sub xxx { 2 };
}

use 5.010;
say ::xxx();      # 0
say ::::xxx();    # 1
say ::::::xxx();  # 2