I wonder why for any line in group "1" (somehow most of them contain a "for"; though a couple are void contexts) Perl sits on unreleased RAM (presumably useful for further, not shown lines of a program); but for any of the "2", the 3d RAM probing reveals the memory was released i.e it's again the initial ~ 10 Mb consumed.

use strict;
use warnings;
use feature 'say';
use Thread::Queue;

sub memory { qx( tasklist/nh /fi "PID eq $$" ) =~ /(\S+ K)$/ }  # Stra
+wberry

my $q = Thread::Queue-> new;
say memory;

{
    my $n = 1e9;
    my $s = 'x' x $n;               # avoid compile-time folding
    $q-> enqueue( $s );
    $q-> end;
}
say memory;

{
    my $tmp; for ( 1 ) { $tmp = $q-> dequeue }                  # 1
    # for ( $q ) { my $tmp = $_-> dequeue }                     #
    # my $tmp; for ( $q ) { $tmp = $_-> dequeue }               #
    # my $tmp; $tmp = $_-> dequeue for $q;                      #
    # $q-> dequeue; $q-> dequeue;                               #
    # $q-> dequeue;                                             #

    # my $tmp = $q-> dequeue;                                   # 2
    # my $tmp; if ( 1 ) { $tmp = $q-> dequeue }                 #
    # my $tmp; do { $tmp = $q-> dequeue }                       #
    # ( my $tmp ) = map $_-> dequeue, $q;                       #
    # 1 while $q-> dequeue;                                     #
}
say memory;

__END__

10,912 K
987,620 K
987,628 K
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