Here's a different approach: adding wrappers to the standard tied routines instead of redefining them:

# usage: tie $var, 'Tie::Scalar::Log', 
#            init value (may be undef), 
#            logfile (string), 
#            varname (string),
#            events  (array or undef);

## Tie::Scalar::Log.pm
package Tie::Scalar::Log;
use Hook::LexWrap;
use IO::File;
use Carp;
require Tie::Scalar;
our @ISA = qw/Tie::StdScalar/;

my %LOG_IT;

wrap Tie::StdScalar::TIESCALAR,
  post => sub {
    my $self = $_[-1];
    my ($logfile,$name,$events) = @_;
    $logfile ||= '';
    my $log = IO::File->new($logfile,'>>');
    if ($log) {
      $LOG_IT{$self} = {name => $name, log => $log};
      $events ||= [];
      $events = [qw/TIESCALAR FETCH STORE DESTROY/] 
        if grep /all/i, @$events or !@$events;
      $LOG_IT{$self}{uc($_)} = 1 for @$events;
      $self->logit("TIESCALAR => $logfile") if $LOG_IT{$self}{TIESCALA
+R};
    } else {
      carp "logfile <$logfile> couldn't be created: variable not tied"
+;
      $_[-1] = undef;
    }
  },
  pre => sub {
    carp q|Wrong number of arguments to tie()|
        and $_[-1] = undef unless @_ == 6
  };

wrap Tie::StdScalar::FETCH,
  post => sub {$_[0]->logit("FETCH => $_[-1]") if $LOG_IT{$_[0]}{FETCH
+}};

wrap Tie::StdScalar::STORE,
  post => sub {$_[0]->logit("STORE => $_[-1]") if $LOG_IT{$_[0]}{STORE
+}};

wrap Tie::StdScalar::DESTROY,
  post => sub {$_[0]->logit("DESTROY") if $LOG_IT{$_[0]}{DESTROY}};

sub logit {
  my ($self, $msg) = @_;
  my $name = $LOG_IT{$self}{name};
  my ($pkg,$file,$line) = caller(1);
  print {$LOG_IT{$self}{log}} "$name => $msg ", 
                              "\t<at $file line $line>\n"
}
1;
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