use Data::Dumper;

 my @a_array = ('apple 2', 'orange 5', 'pear 3',);
 my @b_array = ('apple', 'apple', 'apple', 'orange', 'orange', 'pear',);

 my @c_array; 

  for my $item_1 (@b_array){
    for my $item_2 (@a_array){
      push @c_array, $item_2 if $item_2=~/^$item_1/;
    }
  }

 print Dumper \@c_array;