I think that construct is still legal in Perl 5.8.x but you may be falling foul of use strict;. I may be wrong but I suspect that your $h contains a string which is the name of another variable thus setting up a soft reference. The following have been run under Perl 5.8.4

Firstly with no use strict; or use warnings;

#use strict;
#use warnings;

$h = "fred";
%$h = (name => "Jim", age => 34);
print $h->{name}, "\n";
print $fred{age}, "\n";
[download]

produces

Jim
34
[download]

Switching on strict like this

use strict;
use warnings;

our %fred;
my $h = "fred";
%$h = (name => "Jim", age => 34);
print $h->{name}, "\n";
print $fred{age}, "\n";
[download]

produces

Can't use string ("fred") as a HASH ref while "strict refs" in use at 
+pbeck2 line 8.
[download]

because use strict; objects to soft references. Only by switching strict off for the duration of a code block can you use soft references.

use strict;
use warnings;

our %fred;
my $h = "fred";
{
    no strict q(refs);
    %$h = (name => "Jim", age => 34);
    print $h->{name}, "\n";
}
print $fred{age}, "\n";
[download]

produces

Jim
34
[download]

I hope this clarifies what might be happening with your "illegal" code.

Cheers,

JohnGG