There is a mistake in the second section of code. It should read like this.

my $re = qr/(?:(simple).*?)+/;
my $string = "This is a simple thing just a simple simple thing.";

$string =~ /$re$re$re/g;

say $1 if $1; # says simple
say $2 if $2; # says simple
say $3 if $3; # says simple
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