Perl/Basics/Loops

A loop is a block of code that continues to execute until a condition is met.

While

• A while loop executes while a condition is true.

my $switch; my $counter; while (undef $switch) { print $counter; $counter++; $switch = 1 if ($counter > 100); }

 The above code will execute until $switch is defined.

It is possible to create an infinite loop using while (1) { ... }.

Until

• An until loop executes until a condition is true.

my $switch; my $counter; until (defined $switch) { print $counter; $counter++; $switch = 1 if ($counter > 100); }

 The above code will execute until $switch is defined.

For

• A for loop has a built-in counter and stops at a pre-defined number.

my @messages = ("Hello world!\n","I like perl!\n"); for (my $counter = 0; $counter < $#array; ++$counter) { print $messages[$counter]; }

 The above code will iterate through every element in an array.

It is possible to create an infinite loop using for (;;) {...}.

Foreach

• A foreach loop is built specifically for array handling and iterates through all of the elements in an array.

my @messages = ("Hello world!\n","I like perl!\n"); foreach my $message (@messages) { print $message; }

 The above code will iterate through every element in an array.