Re: Unusual Closure Behaviour

[artist]

HI, Try this, Here it says that $x is not defined and therefore it creates a new local variable $x with 'my'.
Otherwise it uses the last value of x which is the default behaviour.

sub foo {
        my $x if !defined $x;
        return ++$x;
}
for (1..7){ print foo(); };

[tye]

Actually, that code isn't doing what you think. One way to see is to just add "use strict" to it. You'll get: Global symbol "$x" requires explicit package name

A more fun way is:

sub foo {
    my $x= $_[0]   if  ! defined $x;
    print "(@_):", ++$x, " ";
    undef $x   if  @_  &&  shift;
}
foo($_) for( 0,0,5,4,3,0,5,0,4,0,3 );
print $/, $x= 10, $/;
foo($_) for( 0,0,5,4,3,0,5,0,4,0,3 );
print $/;

which produces:

(0):1 (0):1 (5):6 (4):5 (3):4 (0):1 (5):6 (0):1 (4):5 (0):1 (3):4
10
(0):1 (0):2 (5):3 (4):1 (3):1 (0):1 (5):2 (0):1 (4):2 (0):1 (3):2

The $x in "if !defined $x" is the global $main::x because my variables can't be used until after the end of the statement in which they were declared.

So your code is always initializing the lexical $x in your subroutine because you have never defined the global $main::x that you are checking against.

        - tye (but my friends call me "Tye")