In the OPed code, the statement
    BEGIN { say __PACKAGE__."::begin $variable"; }
refers to the lexical  $variable scalar, but the  BEGIN block executes first, after the  $variable is declared, but before it is initialized at run time. Hence, it is uninitialized, but still consistent with strict. Changing the variable name makes this clear:

c:\@Work\Perl\monks>perl -wMstrict -le
"use strict;
 use warnings;
 use feature 'say';
 ;;
 Foo->test('xxx');
 ;;
 {
   package Foo;
   ;;
   my $variable = 'bar';
   ;;
   BEGIN { say __PACKAGE__ . qq{::begin $vaRRRRiable}; }
   ;;
   sub test { say $_[0], $_[1], $variable; }
   }
 ;;
 Foo->test('yyy');
"
Global symbol "$vaRRRRiable" requires explicit package name at -e line
+ 1.
BEGIN not safe after errors--compilation aborted at -e line 1.
[download]

c:\@Work\Perl\monks>perl -wMstrict -le
"use strict;
 use warnings;
 use feature 'say';
 ;;
 Foo->test('xxx');
 ;;
 {
   package Foo;
   ;;
   my $variable = 'bar';
   ;;
   BEGIN { say __PACKAGE__ . qq{::begin $variable}; }
   ;;
   sub test { say $_[0], $_[1], $variable; }
   }
 ;;
 Foo->test('yyy');
"
Use of uninitialized value $variable in concatenation (.) or string at
+ -e line 1.
Foo::begin
Use of uninitialized value $variable in say at -e line 1.
Fooxxx
Fooyyybar
[download]

clear and neat explication, as always AnomalousMonk

this kind of problems happened to me too some time (years?) ago until i realized the right order.

my $variable  = 'value';
-----------  ---------- 
| 1          | 3

BEGIN{ say $variable}
---------------------
| 2
[download]

As the OP reveals, the compiletime runtime order implication is not so easely intellegible from docs: maybe is worth to put a note in perlmod where BEGIN block is described (well i do not understand why it is here, anyway; a separtate tutorial about the phases of the Perl process would not be better?).

The OP can profits the read of some stuffs about the matter:

• Re: RunTime & compile Time Doubt on Perl (many)
• Context: compile-time vs. run-time
• Re^2: Understanding compiletime vs. runtime
• Re^3: Perl compiler request - flogging the dead horse!
• ikegami on SO about runtime compiletime
• perldoc about BEGIN blocks

L*

There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.

this kind of problems happened to me too ...

You and me both, brother. And thank you for the compliment.

---

Give a man a fish:  <%-{-{-{-<

BEGIN blocks run before the rest of the code in the module is even interpreted, so at the time when BEGIN { say __PACKAGE__."::begin $variable"; } runs, the lexical variable $variable has not been created, so the global variable of that name is used, and it has no value; hence the warning.

Solution: don't close over lexical variables in BEGIN blocks.

lexical variable $variable has not been created, so the global variable of that name is used

Um ,no: the BEGIN block sees the lexical var, not the package var:

$x = 'pkg';
my $x;
BEGIN { $x = 'lex' }
print "$::x $x\n"; #prints pkg lex
[download]

Dave.

Intriguing.

So by the time the BEGIN block runs, perl knows enough to know that there is(will be) a lexical $x, sufficient to be able to assign to it; but not enough to have initialised it.

That's just weird!

---

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