There are a number of built-ins that you can override (see perlsub). However, print is one of the built-ins that doesn’t work this way. The difficulties of overriding print are detailed at this perlmonk’s thread. However, you can Create a package Tie a handle Select this handle. Now, a couple of people have given the … Read more
Nice project, here are a few: scalar x!! $value # conditional scalar include operator (list) x!! $value # conditional list include operator ‘string’ x/pattern/ # conditional include if pattern “@{[ list ]}” # interpolate list expression operator “${\scalar}” # interpolate scalar expression operator !! $scalar # scalar -> boolean operator +0 # cast to numeric … Read more
my restricts the scope of a variable. The scope of a variable is where it can be seen. Reducing a variable’s scope to where the variable is needed is a fundamental aspect of good programming. It makes the code more readable and less error-prone, and results in a slew of derived benefits. If you don’t … Read more
From perlfaq8‘s answer to How do I start a process in the background? Several modules can start other processes that do not block your Perl program. You can use IPC::Open3, Parallel::Jobs, IPC::Run, and some of the POE modules. See CPAN for more details. You could also use system(“cmd &”) or you could use fork as … Read more
The right way to do it — by an order of magnitude — is to use Text::CSV_XS. It will be much faster and much more robust than anything you’re likely to do on your own. If you’re determined to use only core functionality, you have a couple of options depending on speed vs robustness. About … Read more
You could have a circular reference in one of your objects. When the garbage collector comes along to deallocate this object, the circular reference means that everything referred to by that reference will never get freed. You can check for circular references with Devel::Cycle and Test::Memory::Cycle. One thing to try (although it might get expensive … Read more
There are no universal standards, but there are reasons to prefer one or another. My preferred form is this: open( my $input_fh, “<“, $input_file ) || die “Can’t open $input_file: $!”; The reasons are: You report errors immediately. (Replace “die” with “warn” if that’s what you want.) Your filehandle is now reference-counted, so once you’re … Read more
Output of perldoc -q round Does Perl have a round() function? What about ceil() and floor()? Trig functions? Remember that int() merely truncates toward 0. For rounding to a certain number of digits, sprintf() or printf() is usually the easiest route. printf(“%.3f”, 3.1415926535); # prints 3.142 The POSIX module (part of the standard Perl distribution) … Read more
Yes, Google is notoriously difficult for looking up punctuation and, unfortunately, Perl does seem to be mostly made up of punctuation 🙂 The command line switches are all detailed in perlrun (available from the command line by calling perldoc perlrun). Going into the options briefly, one-by-one: -p: Places a printing loop around your command so … Read more
Best practices: avoid the shell, use automatic error handling – IPC::System::Simple. require IPC::System::Simple; use autodie qw(:all); system qw(command –arg1=arg1 –arg2=arg2 -arg3 -arg4); use IPC::System::Simple qw(runx); runx [0], qw(command –arg1=arg1 –arg2=arg2 -arg3 -arg4); # ↑ list of allowed EXIT_VALs, see documentation Edit: a rant follows. eugene y’s answer includes a link to the documentation to system. … Read more