OK Im a little confused now - I see where and why he is getting his error above and that $_ is undefined. In my example below - I see the first print statement which I beleive to be equivelant to the ops print statement. But Im confused about my second print statement - where and how is $_ getting set? Is split setting it?

from perldoc -f split:

If EXPR is omitted, splits the $_ string.  If PATTERN is also omitted,
+ splits on whitespace (after skipping any leading whitespace).  Anyth
+ing matching PATTERN is taken to be a delimiter separating the fields
+.  (Note that the delimiter may be longer than one character.)
[download]

EXPR is not omitted, PATTERN is not omitted - where is $_ coming from? Is there some documentation someone can point out that explains this behavior?

#!/usr/bin/perl
use warnings;
use strict;

print "$_\n" for split ( "Hello World" );
 
print "$_\n" for split /\s+/, "Hello World";
[download]

UPDATE
OK I see in perlvar that for is setting it and split is not my culprit.

Here are the places where Perl will assume $_ even if you don't use it
+:
__snip__
- The default iterator variable in a foreach loop if no other variable
+ is supplied.
[download]

But why is for not setting it in the first print statement?

UPDATE #2
from the following looks like $_ is an empty hash?

#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;

print "\n\n";
print "\$_ = $_\n";

print "\n\n";
for ( 1 .. 10 ) { print "\$_ = $_\n" }

print "\n\n";
print $_ for {};

print "\n\n";
print Dumper $_ for {};

print "\n\n";
my $count = 0;
for ( sort keys %{ $_ } ) { print $count++, ":$_{$_} $_\n" };
[download]

Now Im really confused.

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