The algorithm is simple. Find all local maxima, for some appropriate definition of a maximum (eg, $_[0] < $_[1] > $_[2] might mean that $_[1] qualifies). Sort that list of maxima by value in descending order. Return the first k entries in the list.

so ...

my @values = qw(1 4 3 2 5 6 3 4 2);
my @maxima = ();
my $k = 2;
foreach my $index (1 .. $#values - 1) {
    push @maxima, $values[$index] if(
        $values[$index-1] < $values[$index] &&
        $values[$index+1] < $values[$index]
    );
}
# @maxima now contains qw(4 6 4);
print join(', ', (sort { $a <=> $b } @maxima)[0 .. $k - 1])."\n";
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Finding the indices of the top k maxima is left as a trivial exercise for the reader (hint: push a structure onto @maxima containing the value and index).