For investigating this further (in Linux):

print "pid:$$\n";
my $x = 'monks' x (3);
sleep 60;
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and then use gcore <pid> to dump the memory of said process to file (called core.<pid>) and then find occurences of "monks" either with strings core.<pid> | grep monks or hexdump -C core.<pid> | grep monks

true to what the explanation offered to perlmonks above, the anonymous monk firstly:

print "$$\n";
my $n = 3;
$x = 'monks' x ($n);
sleep 60;
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monksmonksmonks
monks
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contrast to

print "$$\n";
$x = 'monks' x (3);  
sleep 60;
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monksmonksmonks
monksmonksmonks
monksmon<
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bw, bliako