use strict;
use warnings;

my @array = qw /aap noot mies wim zus jet teun vuur gijs lam kees bok weide does hok duif schapen/;
my $counter = -1;

@array = @array[grep {$_} map {$counter++; /a/ ? undef : $counter;} @array];

{ local $, = '|'; print @array; }