CODEWITHSUNDEEP
perlloopsbreakstrict
Zain Rizvi
Zain Rizvi

Reputation: 24666

How do I break out of a loop in Perl?

I'm trying to use a break statement in a for loop, but since I'm also using strict subs in my Perl code, I'm getting an error saying:

Bareword "break" not allowed while "strict subs" in use at ./final.pl line 154.

Is there a workaround for this (besides disabling strict subs)?

My code is formatted as follows:

for my $entry (@array){
    if ($string eq "text"){
         break;
    }
}

Upvotes: 331

Views: 630368

Answers (5)

Zain Rizvi
Zain Rizvi

Reputation: 24666

Oh, I found it. You use last instead of break

for my $entry (@array){
    if ($string eq "text"){
         last;
    }
}

It's also described under Loop Control in "perlsyn(1)" (man perlsyn on UNIX-like).

Upvotes: 482

Timur Shtatland
Timur Shtatland

Reputation: 12465

For Perl one-liners with implicit loops (using -n or -p command line options), use last or last LINE to break out of the loop that iterates over input records. For example, these simple examples all print the first 2 lines of the input:

echo 1 2 3 4 | xargs -n1 | perl -ne 'last if $. == 3; print;'
echo 1 2 3 4 | xargs -n1 | perl -ne 'last LINE if $. == 3; print;'
echo 1 2 3 4 | xargs -n1 | perl -pe 'last if $. == 3;'
echo 1 2 3 4 | xargs -n1 | perl -pe 'last LINE if $. == 3;'

All print:

1
2

The perl one-liners use these command line flags:
-e : tells Perl to look for code in-line, instead of in a file.
-n : loop over the input one line at a time, assigning it to $_ by default.
-p : same as -n, also add print after each loop iteration over the input.

SEE ALSO:

last docs
last, next, redo, continue - an illustrated example
perlrun: command line switches docs

More examples of last in Perl one-liners:

Break one liner command line script after first match
Print the first N lines of a huge file

Upvotes: 3

Kamal Nayan
Kamal Nayan

Reputation: 1960

Simply last would work here:

for my $entry (@array){
    if ($string eq "text"){
         last;
    }
}

If you have nested loops, then last will exit from the innermost loop. Use labels in this case:

LBL_SCORE: {
    for my $entry1 (@array1) {
        for my $entry2 (@array2) {
            if ($entry1 eq $entry2) { # Or any condition
                last LBL_SCORE;
            }
        }
    }
 }

Given a last statement will make the compiler to come out from both the loops. The same can be done in any number of loops, and labels can be fixed anywhere.

Upvotes: 25

MortenB
MortenB

Reputation: 3567

On a large iteration I like using interrupts. Just press Ctrl + C to quit:

my $exitflag = 0;
$SIG{INT} = sub { $exitflag=1 };

while(!$exitflag) {
    # Do your stuff
}

Upvotes: 5

Kent Fredric
Kent Fredric

Reputation: 57414

Additional data (in case you have more questions):

FOO: {
       for my $i ( @listone ){
          for my $j ( @listtwo ){
                 if ( cond( $i,$j ) ){

                    last FOO;  # --->
                                   # |
                 }                 # |
          }                        # |
       }                           # |
 } # <-------------------------------

Upvotes: 180

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