sub display_values_from_file {
  my $filename = shift;
  if(open FILE, "<$filename") { # check return value of open
    flock FILE, 1;
    while(<FILE>) {
      print &process_line_from_file;
    }
    close FILE;
  } else {
    print "The file could not be opened. Please try again later!";
    log_error "open $filename : $!";
  }
}
# main program
... # do something
print $some_nice_html;
display_values_from_file "/foo/bar.baz";
print $rest_of_html_page;
# end