Re^2: How many loops are there in Perl?

... the naked-block isn't a loop ... without a label and goto[.]

Or at least a (possibly conditional) redo (see also Loop Control):

perl -wMstrict -le
"my $i = 1;  { print qq{in naked loop $i};  redo if $i++ < 3; }
"
in naked loop 1
in naked loop 2
in naked loop 3
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Comment on Re^2: How many loops are there in Perl? Download Code

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Re^3: How many loops are there in Perl? by adamcrussell (Hermit) on Jan 31, 2012 at 22:14 UTC
I have always thought redo was cool. At first glance it doesn't look anything like a goto because it is usually used with bare blocks. The code below has redo going to the start of the nearest enclosing block. `{ print "Enter a number 0-9\n"; $number=<STDIN>; chomp($number); unless(length($number) == 1 && $number =~ /[0-9]/){ print "C'mon, man! give me a number 0-9!\n"; redo; } }` [download] However, redo can take an argument (a block label) which makes it look much more goto-ish and less like elegant Perl. For example, we could redo (pun intended!) the example like this: `GET_NUMBER:{ print "Enter a number 0-9\n"; $number=<STDIN>; chomp($number); unless(length($number) == 1 && $number =~ /[0-9]/){ print "C'mon, man! give me a number 0-9!\n"; redo GET_NUMBER; } }` [download] The biggest difference between redo and a pure goto is that redo must go to an enclosing block label whereas goto goes to any label. This is still a valid redo: `my $number; PROMPT_FOR_NUMBER:{ print "Enter a number 0-9\n"; GET_NUMBER:{ $number=<STDIN>; chomp($number); unless(length($number) ==1 && $number =~ /[0-9]/){ print "You don't want to give me one number ?\n"; redo PROMPT_FOR_NUMBER; } } }` [download] <jc> Why do people persist in asking me stupid questions? <Petruchio> <insert mutually recursive response> --an exchange from #perlmonks on irc.slashnet.org(2 March 2009 1345 EST)	[reply] [d/l] [select]

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Re^3: How many loops are there in Perl?
by adamcrussell (Hermit) on Jan 31, 2012 at 22:14 UTC

{
    print "Enter a number 0-9\n";
    $number=<STDIN>;
    chomp($number);
    unless(length($number) == 1  && $number =~ /[0-9]/){
        print "C'mon, man! give me a number 0-9!\n";  
        redo;  
    }
}
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GET_NUMBER:{
    print "Enter a number 0-9\n";
    $number=<STDIN>;
    chomp($number);
    unless(length($number) == 1  && $number =~ /[0-9]/){
        print "C'mon, man! give me a number 0-9!\n";  
        redo GET_NUMBER;  
    }
}
[download]

my $number;  

PROMPT_FOR_NUMBER:{
        print "Enter a number 0-9\n";
        GET_NUMBER:{
            $number=<STDIN>;
            chomp($number);
            unless(length($number) ==1  && $number =~ /[0-9]/){
                print "You don't want to give me one number ?\n";  
                redo PROMPT_FOR_NUMBER;
            }
        } 
}
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<jc> Why do people persist in asking me stupid questions?
<Petruchio> <insert mutually recursive response>
--an exchange from #perlmonks on irc.slashnet.org(2 March 2009 1345 EST)

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