how to write script usage sub routine for the perl file?

[perlanswers]

How can i write the usage function to run the file in perl.

./html.pl -root="/home/data/multiple/" -out="/home/data/output" -file=
+"/home/data/file.txt"

I have the above perl file.I have to run the same file in the terminal as i mentioned above.How can i include usage of the script inside the perl file.
code which i have tried

use strict;
use warnings;
use Getopt::Long qw(GetOptions);
sub usage {
   if (@_) {
      my ($msg) = @_;
      chomp($msg);
      print(STDERR "$msg\n");
   }

GetOptions(
       'root=s' => \my $dir,
    'out=s' => \my $out,
    'file=s' => \my $file,
)
    or usage();

[Discipulus]

Hello perlanswers and welcome to the monastery and to wonderful world of Perl!

There are many way to do it but I found the following particulary useful and versatile: The Dynamic Duo --or-- Holy Getopt::Long, Pod::UsageMan!

Infact Pod::Usage can semplfy a lot such part of a program: it can shows sections of your choice of the POD embed in the program (I'm used to put the POD after the __DATA__ token), it has the ability to modify the exit value with the useful NOEXIT feature.

The module can semplify a lot the help and manual commandline options; let's see it's recommendend usage:

use strict;
use Pod::Usage;
use Getopt::Long;
 
## Parse options
my %opt;
GetOptions(\%opt, "help|?", "man", "flag1")  ||  pod2usage(2);
pod2usage(1)  if ($opt{help});
pod2usage(-exitval => 0, -verbose => 2)  if ($opt{man});
 
## Check for too many filenames
pod2usage("$0: Too many files given.\n")  if (@ARGV > 1);

L*

[huck]

Friend of yours? Re^2: How to read the input directory from command line arguments using perl?

[marto]

Looks like the same person.

[LanX]

Yes!

[Anonymous Monk]

From looking at the code, the usage function expects an argument. But, none is given.

    ... or usage();