How come perl cannot last i.e. break for label in the front ahead ? How should the correct syntax be ?

my $f;my $err=9;
my @l=(7,8,9,10);
for (@l) { 
  last T if $_==$err
}
$f=@l;
print "\ncomplete";
T:
print "\ncontain error";

Label not found for "last T" at ./non.pl line 17 

CodePudding user response：

To use last T, you need to be inside of a loop with the label T.

To do what it looks like you want to do, the correct syntax is

goto T if $_==$err

CodePudding user response：

• return exits scopes until a sub call is found,
• die exits scopes until an eval is found, and
• last, next and redo exit scopes until an loop is found.

To jump ahead, use goto.

goto T if $_ == $err;

But wouldn't this be clearer:

my @l = ( 7, 8, 9, 10 );

my $err = 9;

my $f;
if ( grep { $_ == $err } @l ) {   # Or `first` from List::Util
   say "contain error";
   $f = undef;
} else {
   say "complete";
   $f = @l;
}

If you plan to check against the same @l many times, this would be better:

my @l = ( 7, 8, 9, 10 );
my %l = map { $_ => 1 } @l;

my $err = 9;

my $f;
if ( $l{ $err } ) {
   say "contain error";
   $f = undef;
} else {
   say "complete";
   $f = @l;
}