Meaning of the perl syntax construction involving a comma

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I've encountered a piece of code in a book that looks like this:

#for (some_condition) {
#do something not particularly related to the question
$var = $anotherVar+1, next if #some other condition with $var
#}

I've got no clue what does the comma (",") between $anotherVar+1 and before next do. How is this syntax construction called and is it even correct?

Consider the following code:

$x=1;
$y=1;

$x++ , $y++ if 0; # note the comma! both x and y are one statement
print "With comma: $x $y\n";

$x=1;
$y=1;

$x++ ; $y++ if 0; # note the semicolon! so two separate statements

print "With semicolon: $x $y\n";

The output is as follows:

With comma: 1 1
With semicolon: 2 1

A comma is similar to a semicolon, except that both sides of the command are treated as a single statement. This means that in a situation where only one statement is expected, both sides of the comma are evaluated.

Semicolons or newlines?, Now, if what you meant is that newlines have syntactic meaning in addition to their ordinary It's fine for folks who want little program structure beyond the statement, perl foo(1,2,3) bar(4,5,6); Semicolon seems to be missing at - line 1. syntax error no construct may involve two adjacent identifiers, so that 'a' after 'y' must� Perl borrows syntax and concepts from many languages: awk, sed, C, Bourne Shell, Smalltalk, Lisp and even English. However, there are some definite differences between the languages. This chapter is designd to quickly get you up to speed on the syntax that is expected in Perl.

The comma operator is described in perlop. You can use it to separate commands, it evaluates its left operand first, then it evaluates the second operand. In this case, the second operand is next which changes the flow of the program.

Basically, this is a shorter way of writing

if ($var eq "...") {
    $var = $anotherVar + 1;
    next
}

The comma can be used in a similar way in C, where you can find it often in for loops:

for (i = 0, j = 10; i < 10; i++, j--)

Perl, User can break or split the string on different characters like comma(,) example there will be 4 values after splitting so here user will define� The Perl language includes a specialized syntax for writing regular expressions (RE, or regexes), and the interpreter contains an engine for matching strings to regular expressions. The regular-expression engine uses a backtracking algorithm, extending its capabilities from simple pattern matching to string capture and substitution.

The comma is an operator, in any context. In list context where it's usually seen, it is one way to concatenate values into a list. Here it is being used in scalar context, where it runs the preceding expression, the following expression, and then returns the following expression. This is a holdover from how it works in C and similar languages, when it's not an argument separator; see https://docs.microsoft.com/en-us/cpp/cpp/comma-operator?view=vs-2019.

my @stuff = ('a', 'b'); # comma in list context, forms a list and assigns it
my $stuff = ('a', 'b'); # comma in scalar context, assigns "b"
my $stuff = 'a', 'b'; # assignment has higher precedence
                      # assignment done first then comma operator evaluated in greater context

Perl, Like other Programming Languages, Perl also follows a basic syntax for writing Variables are user-defined words that are used to hold the values passed the Run-time. every statement in Perl must end with a semicolon(;). Above block holds statements that have their operations related to each other. Perl Syntax Overview Statements . Each statement in Perl must end on a semicolon. Statements can be spread over several lines. Spacing and indentation is for the most part ignored by Perl and should be used to make the program more readable. (See the <<EOF construction for the one case where spacing can't be ignored.)

Fat comma, Using a fat comma to bind key-value pairs in a hash, instead of using a comma, is considered an example of good idiomatic Perl. In CoffeeScript and TypeScript,� 2 Rearrange print order of key-value data read from file in Perl Jul 20 '19 2 Handle multiple arguments to a Perl subroutine Jul 21 '19 2 Meaning of the perl syntax construction involving a comma Feb 1

Semicolon, The semicolon or semi-colon ; is a symbol commonly used as orthographic punctuation. In the For example, the first edition of The Chicago Manual of Style (1906) the semicolon is called Fasila Manqoota (Arabic: فاصلة منقوطة) which means Therefore, semicolon provides structure to the programming language. The second standard trick to perl one-liners are the -n and -p flags. Both of these make perl put an implicit loop around your program, running it once for each line of input, with the line in the $_ variable. -p also adds an implicit print at the end of each iteration. Both of these use perl's special "ARGV" magic file handle internally.

Note that Perl character class matching is based on the locale model of the operating system, whereas Oracle Database regular expressions are based on the language-specific data of the database. In general, a regular expression involving locale data cannot be expected to produce the same results between Perl and Oracle Database.

Comments
  • You mean the comma operator? You can use it as an alternate statement separator which is what seems to be happening here, but it's not the best idea. Use ; and a new statement instead.
  • I prefer the longer version (using a block with one statement per line). If you crammed 2 statements into the "if", chances are high that you will need to add more. The longer form is more clear and maintainable.
  • @Timur Shtatland, Even worse is that it hides a flow control change (next).