Your $two isn't tainted because it is not really user data or derived from user data (but it is set based upon the presence of the option). Try changing it to accept a string parameter to see what happens: 

GetOptions('b=s' => \$two);
...

./script.pl -b foo

[download]

I'm not sure why your CGI param is not tainted, mine is (CGI.pm version 2.752).

-derby

update: As for the CGI param not being tainted, when you run under "offline mode", CGI reads from STDIN and passes the data to shellwords (shellwords.pl). shellwords parses the passed data via regex and builds the return value via regex matches - effectively untainting the param. As others have shown, by passing the param on the cmdline (instead of offline), shows the param as tainted.

In reply to Re: variable I expect to be tainted isn't: possible explanations? by derby
in thread variable I expect to be tainted isn't: possible explanations? by kudra

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