use Data::Dumper;
use Devel::Peek;

my $foo = { num => 123.1 };
Dump $foo->{num};

my $serialised = Dumper $foo;
$foo = eval $serialised;   # deserialise
Dump $foo->{num};

__END__
SV = NV(0x669d40) at 0x63c430
  REFCNT = 1
  FLAGS = (NOK,pNOK)
  NV = 123.1               <-- originally, it's a number

SV = PV(0x63d918) at 0x742c80
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x6650d0 "123.1"\0  <- it's a string now, when deserialised...
  CUR = 5
  LEN = 8