Assignment of subroutine references in Perl script

Question

I'm learning Perl from Intermediate Perl by Randal Schwartz. Can somebody explain the assignment of the variables $callback and $getter in the following code?

use File::Find;
sub create_find_callbacks_that_sum_the_size {
my $total_size = 0;
return(sub {$total_size += -s if -f}, sub { return $total_size });
}

my %subs;
foreach my $dir (qw(bin lib man)) {
my ($callback, $getter) = create_find_callbacks_that_sum_the_size( );
$subs{$dir}{CALLBACK} = $callback;
$subs{$dir}{GETTER} = $getter;
}

for (keys %subs) {
  find($subs{S_}{CALLBACK}, $_);

for (sort keys %subs) {
my $sum = $subs{$_}{GETTER}->( );
print "$_ has $sum bytes\n";
}

Am I right in thinking that $callback gets the value of the first subroutine reference:

sub {$total_size += -s if -f}

And that $getter gets the second subroutine reference:

sub { return $total_size }

Is this a list assignment?

many thanks

brian d foy · Accepted Answer · 2018-01-25 13:23:01Z

2

This is a list assignment. The subroutine returns two things. The first thing goes into $callback and the second thing goes into $getter:

my ($callback, $getter) = create_find_callbacks_that_sum_the_size( );

So, yes, your answer is right. Each ends up with one of the anonymous subroutines created in the create_find_callbacks_that_sum_the_size factory.

answered Jan 25, 2018 at 13:23

brian d foy

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