What you call a hash actually seems to be at least one array of arrays. And giving us a dump of your datastructure is a good idea, but it works better if you pass a reference (by adding \ in front of your variables) rather than the hash or array directly. In your case that would probably be something like :

use Data::Dumper;
my @array = somecode();
print Dumper \@array;
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or if you actually have a hash: print Dumper \%hash; this will ensure that your list or hash element is transmitted whole, and not flattened into several arguments.

I'd add perldsc to mtmcc's answer, to obtain a better understanding of Perl data structures. And most of times in Perl, you don't have to use indexes to iterate through an array, you can just write

 for my $element (@f)
{
   my $key = $element->[0];
   ...
}
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.