package SF;

use strict;
use warnings;

use overload
    '.' => 'catSF';

sub new {
    my ($class, $str, $list) = @_;

    return bless {str => $str, list => $list}, $class;
}


sub catSF {
    my ($lhs, $rhs) = @_;

    $lhs = SF->new ("$lhs") if defined $lhs && ! ref $lhs;
    $rhs = SF->new ("$rhs") if defined $rhs && ! ref $rhs;
    $lhs = SF->new ("$lhs") if defined $lhs && ! $lhs->isa ('SF');
    $rhs = SF->new ("$rhs") if defined $rhs && ! $rhs->isa ('SF');
    return SF->new ("$lhs->{str}$rhs->{str}", $lhs->{list}, $rhs->{list});
}


package main;

my $name = SF->new ('GrandFather', [1, 2, 3]);
my $catStr = "Name is $name";

print ref $catStr;