Perlsecret – Perl secret operators and constants

▲ Perlsecret – Perl secret operators and constants(metacpan.org)

67 points by mjs 6 days ago | 22 comments

▲ teach 6 hours ago | parent | next [-]

Perl was the first language I learned on my own after graduating university many years ago. I fell in love with it because of quirks like these and because code written in it can have a poetic quality you don't see often.

Now I am old and joyless and I want the code I write for work to be boring and unsurprising.

But sometimes one can still want to write poetry.

	▲	jrockway an hour ago \| parent \| next [-]
		Perl was also my first productive language, and I do miss it a little. Write something like []string{"foo", "bar", "baz"} in go and you really appreciate qw(foo bar baz). Perl was always designed to be easy to type in, and maybe not so easy to maintain later. Good memories, but not for me anymore.
	▲	wvenable 5 hours ago \| parent \| prev \| next [-]
		This isn't the first time I've said this but also had an early-career job writing Perl code. And I actually got to the point where I liked it -- I mean I could see why it had a following. Subsequently I've written code in almost every popular programming language and I will frequently go years between languages but even so I have very little trouble picking them back up. Even C++. But not Perl. It's just so weird with so many idiosyncrasies that I just can't remember it.
	▲	rcyeh 3 hours ago \| parent \| prev \| next [-]
		Agreed! I learned Perl after trying C; and after struggling with `scanf` (not even getting to tokenization), the ease and speed of `while (<>) { @A = split;` for text-handling made it easy to fall in love. This (in the mid 90s, before Java, JavaScript, and C++ TR1) was also my first contact with associative arrays. I was also drawn to the style of the Camel Book. More than most other languages, Perl encouraged one-liners. When I later read PG's "Succinctness is power" essay, I thought of Perl. https://paulgraham.com/power.html
	▲	pavel_lishin 6 hours ago \| parent \| prev \| next [-]
		I'm having to write a lot more perl at work than I would prefer to. It's still poetry, I suppose, but mostly of the bathroom-stall variety.
	▲	ktpsns 6 hours ago \| parent \| prev \| next [-]
		I discovered Perl directly after PHP before Web 2.0 days. Compared with the extreme, Java or (contemporary) Go, Perl codes (can) have a soul. Interestingly, modern ECMAScript (JS) brought in a few of the nice breweties from Perl world which I haven't seen a long time.
	▲	publicdebates 2 hours ago \| parent \| prev [-]
		Please show me an example of Perl that looks beautiful. I don't believe you.

▲ bolangi 5 hours ago | parent | prev | next [-]

After first experiences with linux shell scripting, sed, awk, and C in 1990s, I found perl a welcome refuge. Way more featureful than DOS .bat files or BASIC! Its capabilities (perl + cpan) have always well exceeded my need for CS goodness. People do complain about the syntax, oddly, without mentioning the numerous ways perl was designed to make common tasks easy to do. The "use strict" pragma, and early adoption of testing culture are two examples where perl led the programming community. With the continued maturing of the language and ecosystem, I can only smile at the naysayers and wish them happiness whatever the language.

▲ omoikane 2 hours ago | parent | prev | next [-]

I didn't know ~- and -~ had a name, I have been using them in many (non-production) places where I wanted to save 2 bytes.

But looks like Perl's implementation is more limited compared to other languages:

    % perl -e 'print ~-(0), "\n"'
    18446744073709551615
    % ruby -e 'print ~-(0), "\n"'
    -1

https://metacpan.org/dist/perlsecret/view/lib/perlsecret.pod...

	▲	shawn_w an hour ago \| parent [-]
		You're not using `integer` in the perl example like you're supposed to. Try `perl -Minteger -E 'say ~-0'` and it should work as expected.

▲ tasty_freeze 6 hours ago | parent | prev | next [-]

They one they named "baby cart" is something I have used to interpolate expressions into a string. Eg

    print "The sum is @{[1+2+3]}";

produces

    The sum is 6

instead of having to do:

    my $sum = 1+2+3;
    print "The sum is $sum";

▲ nineteen999 17 minutes ago | parent | prev | next [-]

Honestly the ones I probably use more than any other? =~ and !~

if ($text =~ /error/) { print "Found error\n"; }

if ($text !~ /error/) { print "No error found\n"; }

It's just fun and fast to slice and dice text this way.

▲ lkbm 3 hours ago | parent | prev | next [-]

> !! Bang bang boolean conversion

This isn't a special operator. This is just how "not" (!) works. In basically every language: C, C++, Javascript, Perl, etc., ! is the "not" operator so !12 gives you false (12 is truthy), and !!12 (not false) gives you true.

It's the same in languages that use different operators for "not". In python, the "not" operator is just the word not, and can write "not not 12" to get True. They didn't implement a special "not not" operator, anymore than Perl implemented a "!!" operator. They just implemented the basic ! / "not" operator.

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stearns 2 hours ago | parent | next [-]

Right, that's the point of TFA. It doesn't list "special" operators, it lists "secret" operators -- that is, operators combined from existing sigils that do clever things.

The "Venus" operator is a good example: it's the '+' addition operator! You just add zero to a value that's coercible into a number.

The Eskimo operators are also interesting: similar to a SQL injection attack, you use a close brace and an open brace to stop and start a new code block from within a string that's sent to the interpreter. Perl didn't invent open and close braces: hence the verb "discover" rather than "implement".

The whole page is a bit of a lark, and a good example of why some of us don't enjoy Perl!

	▲	lkbm 2 hours ago \| parent [-]
		Fair point. I should've read more before jumping in here with my first reaction.

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johnisgood 3 hours ago | parent | prev [-]

Keep in mind that applying the logical NOT operator twice (using `!!`) converts any integer expression into a strict boolean.

Any non-zero value becomes `1`, and zero remains `0`. This is commonly used for boolean normalization when the original expression yields a bitmask or arbitrary integer.

While the same result can be written as `(x != 0)`, the `!!x` idiom is concise, widely used in low-level C code, guarantees a result of exactly `0` or `1`, and works well in macros and constant expressions.

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lkbm 2 hours ago | parent [-]

Fair, I forgot that C bools are just 0 and 1. That's where I first learned the !! trick, but it's been many a year.

	▲	defrost an hour ago \| parent [-]
		Err, C bools have two interpreted values, TRUE, and FALSE. Confusingly (to some) they are integers and while 0 represents FALSE, any non 0 value represents TRUE. It's pedantic, apologies, but that is why the GP refers to "convert to strict boolean"

▲ aldousd666 6 hours ago | parent | prev | next [-]

fun thing about this page: i have gemini in the browser and when I asked it 'why is the entire Wall Family naming these things?' it said it couldn't engage. Turns out 'goatse' is a forbidden word to Gemini.

▲ grumpymuppet 3 hours ago | parent | prev | next [-]

Perk is... quite a thing. I think if you like programming because you like believing you have secret knowledge... go for it. Perk will scratch that itch. But I do not believe it beings you closer to the pantheon of God's. Ai n't gonna stop anyone from dancing with the Satyrs though, if that's your jam.

▲ hekkle 5 hours ago | parent | prev | next [-]

OMG! The Goatsie operator =( )= is WILD! wilder than the glob wild operator *

▲ effnorwood an hour ago | parent | prev [-]

Secret open source. Wait.