in reply to hash from sub directly into foreach loop

First of all, the syntax in the sub is incorrect:
%s{'a'} = 10 ;
%s{'b'} = 20 ;
%s{'c'} = 30 ;

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should be 
$s{'a'} = 10 ;
$s{'b'} = 20 ;
$s{'c'} = 30 ;

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anyway, the following change will work for you: 
#!/usr/bin/perl
use strict  ;
use warnings ;


foreach ( keys %{&testa} ) {
    print "key is $_\n" ;
}

sub testa {
    my $s = () ;
    $s->{'a'} = 10 ;
    $s->{'b'} = 20 ;
    $s->{'c'} = 30 ;

    return $s ;
}

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hope this helps,
davidj

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Re^2: hash from sub directly into foreach loop
by GrandFather (Saint) on Jun 30, 2006 at 11:30 UTC

    Note that:

        my $s = ();

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    is equivelent to

        my $s = (undef);

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    which is equivelent to:

        my $s;

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    The first use of a hash ref autovivifies the referred hash making the previous assignment redundant (and misleading). Consider:

    use strict;
use warnings;
use Data::Dump::Streamer;

my $s = ();
Dump ($s);
$s->{'a'} = 10 ;
Dump ($s);

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    which prints:

    $VAR1 = undef;
$HASH1 = { a => 10 };

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    and note that the contents of $s changes from an undefined value to a hash ref.

    If you really want to indicate intent with an assignment use:

        my $s = {};

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    DWIM is Perl's answer to Gödel
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Re^2: hash from sub directly into foreach loop
by jeanluca (Deacon) on Jun 30, 2006 at 08:23 UTC
    nope, the sub should return a hash and not a hash reference. It should be the same as with 
    foreach( keys CGI::Vars() )

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    because that is what I'm trying to do!

    LuCa
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[d/l]

      You can't "return a hash" from a subroutine, you can only return a list, the effect of return %hash is to flatten the hash into a list of key => value pairs. Thus the effect of the the three following subroutines is similar (the order of the hash keys in the first aside:) 

      sub foo
{
    my %foo = ( Foo => '1',
                Bar => '2');
    return %foo;
}
                                                                      
+          
sub bar
{
   my @bar = qw(Foo 1 Bar 2);
   return @bar;
}
                                                                      
+          
sub baz
{
   return 'Foo','1','Bar','2';
}
                                                                      
+          
print foo(),"\n";
print bar(),"\n";
print baz(),"\n";

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      This is why people are telling you to return a hash reference as this is the only way to retain the, er, hashiness after the appropriate dereferencing.

      /J\

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      Please show working code which does what you're trying to do. When I try the following, it doesn't work:

      Q:\>perl -MCGI -le "foreach( keys CGI::Vars() ) { print }"
Type of arg 1 to keys must be hash (not subroutine entry) at -e line 1
+, near ") ) "
Execution of -e aborted due to compilation errors.

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      When I try the following, which the documentation and davidj suggest, it works (in the sense of not being a syntax error). But that works by returning a hash reference:

      Q:\>perl -MCGI -le "foreach( keys %{ CGI::Vars() }) { print }"

Q:\>

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