Lots of things wrong with your sample code - but probably the most crucial, is that it contains a number of basic syntax problems, and so would never have actually run.

Perhaps you want something like:

use strict;

# Note how a constructor is called
# Classname->new() NOT Classname::new()
my $Mref = Manager->new();

# Prints the value of var for $Mref using an accessor method
print $M1->var, "\n";
print $M1->var("peaches"), "\n";

# Each instance has its own var
my $M2 = Manager->new();
$M2->var("apples");

############## Manager.pm #########
package Manager;
use strict;

# reworked constructor
sub new {
  my $class = shift;   # first arg is name of class

  # create anon hash containing member var
  # and bless into class...
  my $self = bless {   
        var => "var initialised",
      }, $class;
  return $self;
}

# return true for successful package initialisation
1;

# set/get accessor for var - 
sub var {
  my $self = shift;
  $self->{var} = $_[0] if scalar @_;
  return $self->{var};
}
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There are many ways to use object orientation, this is just one of them...