# This is equivalent to 'use Pod::Usage;', except that it does not fail if the
# module is not available:
eval { require Pod::Usage; import Pod::Usage; };

#....

# Usage just calls pod2usage, except in case the Pod::Usage module is not
# available. Then it tries to give some hint on what's going on.
#
sub usage {
  if (defined *pod2usage{CODE}) {
    pod2usage (@_);
  }
  else {
    print STDERR "Can't print error message because the ",
                 "Pod::Usage Perl module is not available\n";
    $"=", ";
    print STDERR "\nAdditional info: @_\n";
    exit 3;
  }