Another way of doing it that maybe slightly faster and use less memory than building a hash or grep. It would also work if the arrays contained duplicates or even compound objects instead of simple string or numbers.

#! perl -slw
use strict;
use constant     ALLPRODUCTS    =>0;
use constant    PROHIBITED    =>1;

my @allProducts = map { int rand 10_000 } 1..1000;
my @selection = map { $allProducts[rand 1000] } 1..50;

sub randProduct (\@\@) {
    local $"="\cA"; #!"
    my ($choice, $disallowed) = ('', "@{$_[PROHIBITED]}");
    $choice = $_[ALLPRODUCTS]->[rand @{$_[ALLPRODUCTS]}] while 1+index
+( $disallowed, $choice );
    return $choice;
}

my $chosen = randProduct @allProducts, @selection;
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