Programming Perl, 4th Edition

redo

redo LABEL
redo

The redo operator restarts a loop block without reevaluating the conditional. The continue block, if any, is not executed. If the LABEL is omitted, the operator refers to the innermost enclosing loop. This operator is normally used by programs that wish to deceive themselves about what was just input:

# A loop that joins lines continued with a backslash
while (<STDIN>) {
    if (s/\\\n$// && defined($nextline = <STDIN>)) {
        $_ .= $nextline;
        redo;
    }
    print;  # or whatever...
}

redo cannot be used to exit a block that returns a value such as eval {}, sub {}, or do {}, and it should not be used to exit a grep or map operation. With warnings enabled, Perl will warn you if you redo a loop not in your current lexical scope.

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 the section Loop Control in Chapter 4.