That is interesting, Ovid. ..and yes, it seems to do the same on my cygwin (though, notice they have updated the Cygwin-Perl significantly in the last several updates of Cygwin). Meanwhile, the following works fine:

use strict;

my %allusers = (
        'users' => {
                'user' => 'Test Account',
                '*Crudles' => 'Hello World',
                'Crud' => 'Another Test',
                '*test' => 'Crud User'
        }
);

foreach my $key (keys %allusers ) {
        delete $allusers {'users'}{$key}
                if '*' eq substr $key, 0, 1;
}
[download]

I think you found a bug worth reporting to the cygwin team, as it does not appear anywhere in the docs there or elsewhere that I can find and appears enough obscure that no one probably noticed...

*G*