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Why does Perl complain "Use of implicit split to @_ is deprecated"?

This code triggers the complaint below:

#!/usr/bin/perl 
use strict;
use warnings;

my $s = "aaa bbb";
my $num_of_item = split(/\s+/, $s) ;
print $num_of_item;

When I run the code, Perl complains that "Use of implicit split to @_ is deprecated" . I really have no "context" for the problem, so I expect you help to explain what's wrong with the code.

Solution

  • You are using split in scalar context, and in scalar context it splits into the @_ array. Perl is warning you that you may have just clobbered @_. (See perldoc split for more information.)

    To get the number of fields, use this code:

    my @items = split(/\s+/, $s);
my $num_of_item = @items;

    or 

    my $num_of_item = () = split /\s+/, $s, -1;

    Note: The three-argument form of split() is necessary because without specifying a limit, split would only split off one piece (one more than is needed in the assignment).