# Change this line from your first snippet...
# my %testHash = ( \@multiKey1 => \@stuff1, \@multiKey2 => \@stuff2, \@multiKey3 => \@stuff3);

# into this:
my %testHash = ( \@multiKey1,  \@stuff1, \@multiKey2, \@stuff2, \@multiKey3, \@stuff3);

# ... and still use this:
use Data::Dumper;
print Dumper \%testHash;

# And run the code.