#declare hash in main 
  my %myhash;

#require the autoloaded modules:
  require ${modulename};
  require ${usermodule};

#build the hash in an autoloaded module using a reference:
 &{${modulename}.'::$modulename'}($param1,\%myhash,\%hash2);

#call another autoloaded module that wants to use the hash:   
  &{${usermodule}.'::$usermodule'}($param1,\%myhash,\$array);

#in $usermodule, keys to the hash exist:
  @mykeys = keys %$hashref;  # is non-empty array

#but any attempt to get hash values produces null. e.g.,
  my $myval = ${hashref}->{$mykeys[0]};