FAQ 3.5: How do I debug my Perl programs?

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3.5: How do I debug my Perl programs?

    Have you tried "use warnings" or used "-w"? They enable warnings to
    detect dubious practices.

    Have you tried "use strict"? It prevents you from using symbolic
    references, makes you predeclare any subroutines that you call as bare
    words, and (probably most importantly) forces you to predeclare your
    variables with "my", "our", or "use vars".

    Did you check the return values of each and every system call? The
    operating system (and thus Perl) tells you whether they worked, and if
    not why.

      open(FH, "> /etc/cantwrite")
        or die "Couldn't write to /etc/cantwrite: $!\n";

    Did you read perltrap? It's full of gotchas for old and new Perl
    programmers and even has sections for those of you who are upgrading
    from languages like *awk* and *C*.

    Have you tried the Perl debugger, described in perldebug? You can step
    through your program and see what it's doing and thus work out why what
    it's doing isn't what it should be doing.


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