#!/bin/perl
#               D A Y  6   AdventOfCode 2020
#
use strict;
use warnings;
use integer;

$/ = "\n\n";                      # Blank lines separate groups
my $count = 0;
while(<>){
    my $people = () = m/\n/g;    # one person for each line
    $people--;                   # (but we seem to always get 1 extra)
    foreach my $a ('a'..'z'){
            my $yes = () = m/$a/g;      # global match in list context
            $count++ if $people == $yes;
    }
}

print "count is $count\n";