while (my ($k, $v) = each %foo) {
  ...
}

##</code><code>##

foreach my $k (keys %foo) {
  my $v = $foo{$k};
  ...
}

##</code><code>##

print join ",", map { &{$field_info{$_}{format}}($deal) } @fields;
print "\n";

##</code><code>##

my @field_subs = map {$field_info{$_}{format}} @fields;
# time passes..
print join ",", map $_->($deal), @field_subs;
print "\n";