use FreezeThaw qw/freeze thaw/;

my $dataStruct;
if (open(DATA, "frozen.data")) {
  my $ice = <DATA>;
  ($dataStruct) = thaw($ice);
  close DATA;
}

# .... do some stuff with $dataStruct

open (DATA, ">", "frozen.data") or die "Failed to write: $!";
print DATA freeze($dataStruct);
close DATA;