A few comments ...

Firstly, hash structures by their nature are unordered lists of scalars - There is no intrinsic order to the index keys which are returned via keys or each. It is discussed in the perldata man page that while a hash may be initialised in a particular order it is no guarentee that iteration of the hash index returns elements in this order - This is also discussed in the perlfunc:keys man page.

If you are wanting a specific order in the hash indices or values returned in a list, you will need to employ the perlfunc:sort function. eg.

#   iterate by sorted list of hash keys
foreach my $key (sort keys %hash) {
    ...
}

#    iterate by sorted list of hash values
foreach my $key (sort { $hash{$b} <=> $hash{$a} } keys %hash) {
    ...
}

[download]

If you are wanting to reverse this sorted order of hash keys or values, you simply need to employ the perlfunc:reverse function. eg.

#   iterate by reverse sorted list of hash keys
foreach my $key (reverse sort keys %hash) {
    ...
}

#    iterate by reverse sorted list of hash values
foreach my $key (reverse sort { $hash{$b} <=> $hash{$a} } keys %hash) 
+{
    ...
}

[download]

 

perl -e 's&&rob@cowsnet.com.au&&&split/[@.]/&&s&.com.&_&&&print'

In reply to Re: running backwards on a hash by rob_au
in thread running backwards on a hash by hotshot

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