1
return \%hash (Note the slash)

2
I'm not sure what you mean with "testing the contents", but Data::Dumper does a nice job of printing out the contents for you.

3
I admit to not having entirely read perldoc DBI (ar0n ducks, thusly avoiding any DBI manuals thrown at him...) so I'm not aware of any such function. But this should work:

my $place_holders = "?," x keys %hash;
chop $place_holders;

my $sth = $dbi->prepare("INSERT INTO my_lovely_table (".join(",", sort
+ keys %hash).") VALUES ($place_holders)");
$sth->execute( @hash{ sort keys %hash } );
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Note though, that the keys in your hashes in your code refer to anonymous arrays (push @{ $hash{$arg} }, split;), so the above won't work with those hashes.

[ar0n]