That's not an an error, that's what each value of the hash holds; a scalar reference to an anonymous array. Consider:-

knoppix@Microknoppix:~$ perl -E '
> %rep  = ( one => 123, two => 456 );
> %comb = ( one => 987, two => 654 );
> %new  = map { $_, [ $rep{ $_ }, $comb{ $_ } ] } keys %rep;
> say qq{$_ => $new{ $_ } => @{ $new{ $_ } }} for keys %new;'
one => ARRAY(0x81a1530) => 123 987
two => ARRAY(0x8195d00) => 456 654
knoppix@Microknoppix:~$
[download]

You have to de-reference the array reference (@{ $new{ $_ } } see perlreftut) to get at the contents.

Update: Added documentation reference.