I don't know what the "naked block" is, but it gets to be very tricky to destroy variables and hashes. First check out Re: undefining hashes to free memory.

In general, you won't be able to completely undefine a hash (memory wise), you can only clear out it's data and keys (but Perl will still retain the allocated memory for future use).

Normally the rule is: you need to undef the variable before it goes out of scope. It works for arrays and strings, but not with hashes.

#!/usr/bin/perl
use strict;
use warnings;
# array reclaims mem 

show_size();

{
    my @var=(0..1000000);
    show_size();
    undef @var;
}

show_size();
exit(0);

sub show_size {
    local $/;
    open(my $pfh, '<', "/proc/$$/status") || die $!;
    my $size = <$pfh> =~ /VmSize:\s+(\d+)/
               ? $1
               : 'unknown';
    close($pfh);
    print "Process size: $size\n";
}
[download]

##############################################

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

# dosn't work well with an hash

show_size();

{
    my %hash;

    for(0..1000000){
      $hash{$_}= 'perlperlperl';
    
    }
    
    show_size();
    
    foreach(0..1000000){
      $hash{$_}= '';
      undef $hash{$_};
    }
    
    undef %hash;
}

show_size();

exit(0);

sub show_size {
    local $/;
    open(my $pfh, '<', "/proc/$$/status") || die $!;
    my $size = <$pfh> =~ /VmSize:\s+(\d+)/
               ? $1
               : 'unknown';
    close($pfh);
    print "Process size: $size\n";
}
[download]

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