We will look at how the contents of this array are constructed and can be manipulated to affect where the Perl interpreter will find module files. Default @INC The Perl interpreter is compiled with a specific default value for @INC. To find this value, run the command env -i perl -V (env -i ignores the … Read more
(This is the official perlfaq answer, minus any subsequent edits) The basic idea of inserting, changing, or deleting a line from a text file involves reading and printing the file to the point you want to make the change, making the change, then reading and printing the rest of the file. Perl doesn’t provide random … Read more
Add the line: $DB::deep = 500; # or more if necessary to the start of your program. The following program runs to completion in the debugger: use strict; use warnings; sub f($) { my $x = shift; print “$x\n”; if ($x < 200) { f(1 + $x); } } $DB::deep = 500; f(1); outputting: 198 … Read more
References, by default, numify to their addresses. Those reference addresses are unique for every reference, so it can often be used in equality checks. However, in the snippet you showed, you’d first have to make sure that both $ref1 and $ref2 are actually references. Otherwise you might get incorrect results due to regular scalars containing … Read more
It converts non-boolean types to boolean (dualvar(0,””) or 1). It is a shortcut way of doing this, instead of trying to cast it explicitly (which may take more characters). The ! operator negates the truthness of its argument. Hence, two of them are used. Many object types are “truthy”, and others are “falsey”. The only … Read more
The use function: use ModuleName; is equivalent to the following code using the require function: BEGIN { require ModuleName; ModuleName->import; } The BEGIN block causes this code to run as soon as the parser sees it. The require loads the module or dies trying. And then the import function of the module is called. The … Read more
The consensus of the Perl community seems to be that Try::Tiny is the preferred way of doing exception handling. The “lenient policy” you refer to is probably due to a combination of: Perl not being a fully object-oriented language. (e.g. in contrast to Java where you can’t avoid dealing with exceptions.) The background of many … Read more
You can use the backtics to execute your external program and capture its stdout and stderr. By default the backticks discard the stderr and return only the stdout of the external program.So $output = `cmd`; Will capture the stdout of the program cmd and discard stderr. To capture only stderr you can use the shell’s … Read more
First off, a subroutine isn’t passed the @ARGV array. Rather all the parameters passed to a subroutine are flattened into a single list represented by @_ inside the subroutine. The @ARGV array is available at the top-level of your script, containing the command line arguments passed to you script. Now, in Perl, when you call … Read more
You should have tried your hunch. That’s how to do it. my $first = (split /\./, “hello.world”)[0]; You could use a list-context assignment that grabs the first field only. my($first) = split /\./, “hello.world”; To print it, use print +(split /\./, “hello.world”)[0], “\n”; or print ((split(/\./, “hello.world”))[0], “\n”); The plus sign is there because of … Read more