stan2004,
Well, you have both done it wrong and done it right. The correct syntax of a for loop of this type is:

# pseudo
for <variable> ( list ) {
   # some code presumably using variable
}

# real
for my $key ( keys %hash ) {
    print "$key\n";
}
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You may omit the <variable> and perl will happily stick the current alias from the list into $_ (see perldoc perlvar).

You have chosen not use warnings and strictures so you didn't get told about the other things you did wrong. This is a testimony to how far Perl will go to do what you mean. The correct way to assign a value to a hash key is:

#psuedo
$hash{<key>} = <value>;

#read
$hash{foo} = 'bar';
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You can however assign multiple values to multiple keys at once using a hash slice. The syntax is

#pseudo
@hash{<list of keys>} = <list of values>;

#real
@hash{ @keys } = @values;
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Finally, keys returns a list of keys in a hash in list context, but the number of keys in scalar context. That is why you got the list of keys. It sounds like you still have a lot to learn. See the various perldocs, check out the tutorials section, check out http://learn.perl.org.