I recommend using indexes of List::MoreUtils to get the indexes and an array slice (Slices) to get the values.

use strict;
use warnings;
use List::MoreUtils qw(indexes);

my @list = qw(1 2 3  4 5 6 7 8 9 8 7 6 5 4 3 2 1);
my $target = 5;
my @indexes = indexes {$_ == $target} @list;
my @values = map {[@list[($_+1)..($_+3)]]} @indexes;
print "@$_\n" foreach @values;
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OUTPUT:

6 7 8
4 3 2
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