use strict;
use warnings;
use Data::Dump;
use List::Util qw/first/;
$\="\n";

# --- init

my @fields = qw( RUN DISTRICT COPY TOTAL );

my %a = map { $_ => 1- int rand 3  } @fields;
my %b = map { $_ => 1- int rand 3  } @fields;

dd \@fields,\%a,\%b;

# ---  w/o List::Util

my $last;
my $field;

for (@fields) {
   $field =$_;
   $last = $a{$_} <=> $b{$_}  and last;
}

print "$field,$last";

# ---  with List::Util


print first { $last = $a{$_} <=> $b{$_} } @fields;
print $last;