(a)
  if ($^O ne "MSWin32") { flock(USERFILE, LOCK_EX); }

    if (@fields[1]=~m/^$loginname$/) {
  if (@fields[2]=~m/^$password$/) {
    $matchokay='true'; # login name matches password
  }
    }

  if ($matchokay) { return $matchokay; }
  else { return ''; }
  

(b)
  flock USERFILE, LOCK_EX if $^O ne 'MSWin32';

    if ( $user =~ m/^$loginName$/) {
      if ( $password =~ m/^$password$/) {
        $matchOkay = 'true';
      }
    }

  if ( $matchokay ) {
    return $matchokay;
  
  } else {
    return '';
  }

Example 2: (a) Poorly indented code; (b) Improved indenting.