Making Perl script *run itself* with flags

Question

I'm very new to Perl, and have recently encountered the following problem. My Perl code must all reside within a single file (it's being called by another program I have no control of). I now wish to make the script run with a flag (e.g., perl myscript.pl -T for taint mode), although it is initially called without the flag. How can I do that, i.e., how do I "set the flag" from within the Perl file?

One idea that I've had is to make the file launch itself again (after being called without flags), this time with the -T flag (by issuing a shell command such as system($^X, "myscript.pl -T", @ARGS);). Would that work? Any better ideas?

Answer 1

I think you're on the right track. You can make use of the $^{TAINT} variable, and exec instead of system:

exec($^X, $0, '-T', @ARGV) if $^{TAINT} < 1;

This won't work in all cases. For one thing, you'll lose some other command line switches that your script might initially be called with:

perl -I/path/to/some/more/libs -w -MNecessary::Module myscript.pl ...

There are some workarounds to some of these (use warnings or add -w switch to your exec statement above, analyze @INC and %INC to determine what -I and -M switches were added) but the more you can learn about exactly how your script is called, the more you can figure out what workarounds you need to worry about.

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Depending on the ... group dynamics in play here, another approach is to exercise some indirect control of the calling program. Go ahead and put -T on the shebang line as @Hunter McMillen and @ThisSuitIsBlackNot suggest, wait for a bug report, and then diagnose the problem as "program not invoked with -T switch" ...