Perl Tidbits: Annoyances and Surprises

Having given up Perl at one time to use Ruby almost exclusively, I have returned to Perl in recent years since Ruby is not available for HP-UX 11i v3 nor for OpenVMS 8.3. Perhaps some Ruby folks are listening; it is abominable that HP-UX 11i has gone without Ruby for so long. It would be nice to be able to say that it is shameful that Ruby doesn’t exist on OpenVMS 8.3 – but we know how popular OpenVMS is…

Here are some of the things I’ve discovered in bits and pieces about Perl since my “return”:

• HP-UX does not use the Perl core, but rather ActiveState Perl. This may not sound like much, but it can be important when using modules. For instance, the Net::FTP module has a bug in it that causes the last character of ASCII transfers to be “snipped”, and several Perl core modules are missing entirely.
• It is possible for Perl to quietly abort without warnings. This makes no sense, but I’ve experienced it. Only stepping through the code with the debugger will show what line it is – and removing the line in question makes the program start working again.
• Using CPAN can corrupt your HP-UX Perl installation. I suspect this is because CPAN assumes that you are using the Perl core, and if not, then things can break. In my case, the module Data::Dumper was hosed so bad I needed to reinstall Perl.
• Perl requires an additional module to emulate Ruby’s p command. This was a real disappointment; attempting to print data in a readable format (no matter what its type) is a simple command in Ruby; in Perl, you must include an additional module and use a function with a confusing name (is it Dump? or is it Dumper? or is it dump?) – I often have to correct my code to use the right one.
• Testing for a module’s existance is easy. Use the command perl -e 'use My::Module;' to see if the module is there.
• Don’t think of $var as the name of a variable, but as the value of a variable. Just this one change in thinking has made a tremendous amount of difference in programming. When you think this way, you see an entry like @myarray[4] for what it is: a list with a single element in it. Likewise, $mine{entry} is a scalar value returned from a hash. The same “variable” can be found with differing leading punctuation based on its value, not on its type.
• If your script needs to be portable across platforms, then write it in Perl. The Korn shell is nice and even more ubiquitous than Perl, and Ruby is (in my opinion, anyway) much nicer than Perl, but Perl is where ksh and Ruby are not. Being there is a significant part of the battle: if that snazzy scripting language isn’t installed, you can’t use it – and Perl is there.
• The documentation (in perldoc) is tremendous! Use perldoc whenever you can: it includes more than a man page would. It includes tutorials, frequently asked questions (FAQs), module documentation, function documentation, and more.

Though I’d still write in Ruby at the drop of a hat, I have indeed rediscovered the joy of Perl. Part of this is due to a book that has illuminated the dusty corners of my knowledge: Effective Perl Programming by Joseph Hall with Randal Schwartz – an awesome book!