How about method-chaining - you can Chain the timeout method when you need it :

use strict;
use warnings;
{package This;

  sub new{ 
    my ($class, %att )=@_;
    return bless {%att}, $class;
  }

  sub with_timeout{
   my ($self, $timeout) = @_;
   $timeout or die "Timeout not specified";
   return bless {%$self, TIMEOUT=>$timeout},__PACKAGE__;
  }

  sub do_work{
      my ($self) = @_;
    for my $k(sort keys %$self){
      print "$k \t=>" . ( $self->{$k}||"Undef*") . "\n";
    }
  }
  1;
}

my $t = This::->new (CANDY=>'Mint');
print "-- First call - no TIME--\n";
$t->do_work();
print "-- adding time--\n";
$t->with_timeout(10)->do_work();
print "-- this should not have it--\n";
$t->do_work();
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