OUTER: foreach my $record (@in) {
    foreach my $field (keys %{$where}) {
      next OUTER unless $record->{$field} eq $where->{$field};
    }
    push @out, $record;
  }

##</code><code>##

$ time perl -e '  my @out = ();

  for my $record (0..10000000) {
    my $keep = 1;
    foreach my $field (qw /80000/) {
      unless ($record == $field) {
        $keep = 0;
        last;
      }
      push @out, $record if $keep;
    }
   }

  print "@out", "\n";'
80000

real    0m4.260s
user    0m4.227s
sys     0m0.015s

##</code><code>##

$ time perl -e '  my @out = ();

  OUTER: for my $record (0..10000000) {
    foreach my $field (80000) {
      next OUTER unless ($record == $field);
    }
    push @out, $record ;
  }

  print "@out", "\n";'
80000

real    0m2.761s
user    0m2.745s
sys     0m0.000s

##</code><code>##


  OUTER: for my $record (0..10000000) {
      next OUTER unless ($record == 80000);
      push @out, $record ;
  }

  print "@out", "\n";'
80000

real    0m0.854s
user    0m0.841s
sys     0m0.000s