This discussion motivated me to dig into tied scalars a little deeper. My goal was to create a tie by which any use of a given scalar would result in a write to a logfile, for debugging purposes. This is very quick and dirty, but here's what I've come up with. I would really appreciate comments that might lead me to improving it.

use strict;
use warnings;

package Trackit;
my $varname;
sub TIESCALAR { 
    my $class = shift; 
    $varname = shift;
    bless \my($self), $class; 
}

sub STORE { 
    ${ $_[0] } = $_[1];
    document ( "STORE", $_[1] );
    return ${ $_[0] };
}

sub FETCH { 
    my $self = shift;
    document( "FETCH", ${$self} );
    return ${ $self } 
}
sub DESTROY {
    my $self = shift;
    document ( "DESTROY", ${$self} );
}
    
sub document {
    my ( $action, $value ) = @_;
    my $fh;
    open $fh, ">>log.txt" or die $!;
    print $fh "$varname => Action: $action, Value = $value\n";
    close $fh;
}

# Begin main ----------------------------
package main;
my $var;
tie $var, "Trackit", '$var';
# Test our handywork...
$var = 10;
$var = $var + 10;
open FH, "<log.txt" or die $!;
while ( <FH> ) {
    print $_;
}
close FH;
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Ok, here are the areas I see a need for improvement. First, it seems kludgy to have to pass as a string the name of the variable we're working with so that it can be printed to the logfile. Next, I haven't provided a way to user-specify the name of the logfile, but that's an easy fix. ...anything else?