I'm afraid that I'm still not clear about what it is that you are trying to do. You mention checking whether or not a variable is defined. Well, Perl has an inbuilt function for this, called defined. A very simple example of its usage is as follows:

#!/usr/bin/perl -l
use strict;
use warnings;

my $foo = 1;
my $bar;

print '$foo is ', defined $foo ? "defined" : "not defined";
print '$bar is ', defined $bar ? "defined" : "not defined";
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$foo is defined
$bar is not defined
[download]

You also mention that you want to track the value of a variable. The easiest way to do this is with print, or perhaps something like Data::Dumper.

If, as apl suggests, you are new to Perl and want to learn, then I would suggest that a good place to start would be the Tutorials section of the Monastery.

In any case, welcome to PerlMonks.

Darren :)