Writes to MongoDB currently aquire a global write lock, although collection level locking is hopefully coming soon. By using more threads you’re likely introducing more concurrency problems as the threads block eachother while they wait for the lock to be released. Indexes will also slow you down, to get the best insert performance it’s ideal … Read more
“Best” is, of course, a matter of taste. Rather than “best”, I’ll answer this as “what editor should I use for Perl if I don’t already have a strong preference for an editor?” I went on a short quest to answer this question for my students. What I recommend now is Atom. It’s free, open … Read more
Use \K as a special case. It’s a variable length positive lookbehind assertion: /eat_(?:apple|pear|orange)_\Ktoday|yesterday/g Alternatively, you can list out your lookbehind assertions separately: /(?:(?<=eat_apple_)|(?<=eat_pear_)|(?<=eat_orange_))today|yesterday/g However, I would propose that it’s going to be a rare problem that could potentially use that feature, but couldn’t be rethought to use a combination of other more common regex … Read more
To get a slice starting with an array reference, replace the array name with a block containing the array reference. I’ve used whitespace to spread out the parts, but it’s still the same thing: my @slice = @ array [1,3,2]; my @slice = @ { $aref } [1,3,2]; If the reference inside the block is … Read more
The character is “\xa0” (i.e. 160), which is the standard Unicode translation for . (That is, it’s Unicode’s non-breaking space.) You should be able to remove them with s/\xa0/ /g if you like.
The use utf8 means Perl expects your source code to be UTF-8. The open pragma can change the encoding of the standard filehandles: use open qw( :std :encoding(UTF-8) ); And, whatever is going to deal with your output needs to expect UTF-8 too. If you want to see it correctly in your terminal, then you … Read more
unless (caller) { print “This is the script being executed\n”; } See caller. It returns undef in the main script. Note that that doesn’t work inside a subroutine, only in top-level code.
perlvar is your friend. It documents all these cryptic special variables. $OUTPUT_AUTOFLUSH (aka $|): If set to nonzero, forces a flush right away and after every write or print on the currently selected output channel. Default is 0 (regardless of whether the channel is really buffered by the system or not; $| tells you only … Read more
The shebang must be the first line because it is interpreted by the kernel, which looks at the two bytes at the start of an executable file. If these are #! the rest of the line is interpreted as the executable to run and with the script file available to that program. (Details vary slightly, … Read more
It depends on what you want to have happen with STDERR and STDOUT. I prefer to send error and warning type messages to STDERR so that when someone is trying to redirect output to a file they still see the error messages; However, there are times though when STDOUT is used to communicate status to … Read more