Re: Bareword Package Names

I'm not sure how documented the behaviour you describe is, but the trailing double colons have another use. Consider the following:

use 5.010;

{
   package Foo;
   sub new { bless [] }
   sub Bar { 'Quux' }
}
{
   package Foo::Bar;
   sub new { bless [] }
}
{
   package Quux;
   sub new { bless [] }
}

my $object1 = Foo::Bar::->new;
say ref $object1;   # says "Foo::Bar"

my $object2 = Foo::Bar->new;
say ref $object2;   # says "Quux"
[download]

perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

Comment on Re: Bareword Package Names Download Code

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Re^2: Bareword Package Names by martin (Friar) on Aug 08, 2012 at 16:16 UTC
What tobyink demonstrated is that a bareword will act as a procedure call if (and only if) a subroutine of that name is known. Perl's auto-quoting of barewords will only kick in in the absence of such a subroutine. Any kind of explicit quoting, of course, will also avoid procedure calls. `my $object3 = 'Foo::Bar'->new; say ref $object3; # says "Foo::Bar"` [download] So we now have established by different examples that trailing double-colons can act like quoting. There may be caveats though. In some places where perl looks for barewords, the package-quoted bareword does not seem to lose its bareword-likeness. `use strict; use warnings; package Foo::Bar; package main; print Foo::Bar::; # warns: # Name "Foo::Bar" used only once: possible typo # print() on unopened filehandle Bar print Foo::Bar::, "Baz\n"; # prints Foo::BarBaz` [download] Perl has to distinguish whether print with a single argument is called as `print HANDLE` or `print LIST`, and apparently uses a rather simple heuristic for this. I try to avoid ambiguity with `print` and always use the `print HANDLE LIST` syntax for printing to handles.	[reply] [d/l] [select]
Re^3: Bareword Package Names by jmlynesjr (Deacon) on Aug 10, 2012 at 03:03 UTC
See Programming Perl 4th Edition page 389 - Symbol Tables. "Symbol tables are stored in a hash whose name is the same as the package, but with two colons appended. The main symbol table's name is thus %main::." "Likewise, the symbol table or the Red::Blue package is named %Red::Blue::." James Also see page 423 - Package-Quoted Classes. "The final syntactic ambiguity with the indirect object style of method invocation is that it may not be parsed as a method call at all, because the current package may have a subroutine of the same name as the method...there is a way to resolve this ambiguity while still keeping the indirect object syntax: package-quote the class name by appending a double colon to it." `$obj = method CLASS::; # forced to be "CLASS"->method`	[reply] [d/l]