Something like this might work:

#!/usr/bin/perl -w 
use strict;
my %seen;
while (<>) { s![\$\%\@]([a-zA-Z]\w*)!$seen{$1}++!eg  }
my @once = sort grep { $seen{$_} == 1 } keys %seen;
if (@once) {
    print "Possible unused variables found: \n\n", join("\n", @once), 
+"\n";
}

[download]

Now, that's hardly foolproof. In any reasonably complicated program it's likely to show a lot of false positives. It might also miss some cases where a variable name is used in more than one type - $foo and @foo for example. A more complicated regex could be devised to deal with that case. Worse, if a variable is declared in multiple scopes but never used then it won't be in the list.

But for your test case it works! If I put my code in use.pl and yours in foo.pl: 

$ perl use.pl foo.pl
Possible unused variables found: 

var_a

[download]

-sam

In reply to Re: Need Unused Variable Warning Msgs by samtregar
in thread Need Unused Variable Warning Msgs by justanyone

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