This isn't really the best way to store/pull back stuff, but it is quick & dirty (basically just eval your $res string):

  # storing:
  my $data = ... ; # some big hairy data structure
  open FILE, ">$filename" or die "can't open '$filename': $!";
  print FILE Dumper($data);
  close FILE;

  # retrieving:
  open FILE, "$filename" or die "can't open '$filename': $!";
  my $VAR1;
  eval do{ local $/=undef; <FILE> };
  # your big hairy data structure is in $VAR1 now
  close FILE;
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You can also play with the Data::Dumper syntax so that the string had "$data =" instead of "$VAR1 =".