Declaring a variable with our effectively creates a package variable (i.e. a typeglob entry) and bequeaths a lexical scope upon the short name symbol. A for() loop aliases it's loop variable, so that our $name loop-variable behaves like a local. That's why declaring $name with our results in $name being undefined after the for() loop run, hence the generated subroutines output an empty $name.

Why does the my-variable version work as expected? - Because the for() loop aliases the my variable as - a my variable. Now, for those the compiler inserts an opcode which clears it after (or before?) every iteration (on ENTER or LEAVE), so that you have a brand new $name (with its own private storage!) each time through the loop.

If you close over a localized our() variable, as per your example, all your generated subs share the same local, which isn't visible outside.

Perl is trying really hard to dwim here, and imho does a good job ;-)

update:

Actually, there's more to it, since the loop variable gets an alias of the list it iterates over. Consider: 

my $name;
for $name (qw(red blue green yellow orange purple violet)) {
  no strict 'refs';        # allow symbol table manipulation
  no warnings 'redefine';  #ignore noise about redefinitions
  *$name = sub {
    my $sOutput = "<FONT COLOR='$name'>@_</FONT>";
    $name = 'something wacky and wonderful'; #change the value
    return $sOutput;
  };
}
print "red:    ${\(red())}\n";
__END__
Modification of a read-only value attempted at - line 7.

[download]

Here the for() iterates over a list of literals, and those are read-only. But! ... 

our $name;
for $name (qw(red blue green yellow orange purple violet)) {
  no strict 'refs';        # allow symbol table manipulation
  no warnings 'redefine';  #ignore noise about redefinitions
  *$name = sub {
    my $sOutput = "<FONT COLOR='$name'>@_</FONT>";
    $name = 'something wacky and wonderful'; #change the value
    return $sOutput;
  };
}
print "red:    ${\(red())}\n";
__END__
red:    <FONT COLOR=''></FONT>

[download]

...why? In this case, the sub closes over the localized $name, which is undefined after the loop finished. That's why you get 

----- sub used inside loop that defined it ------
trying out something wacky and wonderful: <FONT COLOR='something wacky
+ and wonderful'></FONT>

[download]

inside the last loop - you had modified $colors[0] in the previous loop.

In reply to Re: How do closures and variable scope (my,our,local) interact in perl? by shmem
in thread How do closures and variable scope (my,our,local) interact in perl? by ELISHEVA

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