Perl 5 version documentation

redo

Perl functions A-Z | Perl functions by category | The 'perlfunc' manpage
  • redo LABEL

  • redo EXPR
  • redo

    The redo command restarts the loop block without evaluating the conditional again. The continue block, if any, is not executed. If the LABEL is omitted, the command refers to the innermost enclosing loop. The redo EXPR form, available starting in Perl 5.18.0, allows a label name to be computed at run time, and is otherwise identical to redo LABEL . Programs that want to lie to themselves about what was just input normally use this command:

    1.     # a simpleminded Pascal comment stripper
    2.     # (warning: assumes no { or } in strings)
    3.     LINE: while (<STDIN>) {
    4.         while (s|({.*}.*){.*}|$1 |) {}
    5.         s|{.*}| |;
    6.         if (s|{.*| |) {
    7.             my $front = $_;
    8.             while (<STDIN>) {
    9.                 if (/}/) {  # end of comment?
    10.                     s|^|$front\{|;
    11.                     redo LINE;
    12.                 }
    13.             }
    14.         }
    15.         print;
    16.     }

    redo cannot return a value from a block that typically returns a value, such as eval {} , sub {} , or do {} . It will perform its flow control behavior, which precludes any return value. It should not be used to exit a grep or map operation.

    Note that a block by itself is semantically identical to a loop that executes once. Thus redo inside such a block will effectively turn it into a looping construct.

    See also continue for an illustration of how last, next, and redo work.

    Unlike most named operators, this has the same precedence as assignment. It is also exempt from the looks-like-a-function rule, so redo ("foo")."bar" will cause "bar" to be part of the argument to redo.