Here's yet another way to do it...

while( my( $key, $value ) = each %db_stru ) {
    print "$key contains tables:\n";
    print "\t$_:" foreach @{$value};
}
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Then there's always the philosophy of 'print seldom, and print late.'

while( my( $key, $value ) = each %db_stru ) {
    my $out = "$key contains tables:\n";
    $out .= "\t$_:" foreach @{$value};
    print "$out\n";
}
[download]

And for those who like to use special variables instead of explicit loops:

{
    local $" = ":\t";
    while( my( $key, $value ) = each %db_stru ) {
        print "$key contains tables:\n\t@{$value}\n"
    }
}
[download]

Enjoy!