Dear monks,

I have a script that splits fasta file into number of chunks.
SYNOPSIS
perl fasta_split.pl --in=input_file --chnb=number_of_chunks --chnm=chunk_name
It works in almost all situations: with options, with extra options (you get help), with --help (you get synopsis, options and arguments), with --man (you get entire pod), with --versions (version of the Perl, program, etc.), except one: I can't get it to work when I start it without arguments or options. For instance:
perl fasta_split.pl
should give usage, but all I get is errors. I used Getopt::Long with Pod::Usage. The part with the
GetOptions(...) or pod2usage(-verbose => 1) && exit;
should print usage without any arguments but it does not.
Could you help me to figure out what I did wrong here?
Here is the full script (error message in pod BUGS section):

#!/usr/bin/env perl
#it splits fasta file (>prot_id\naaseq\n) into smaller chunks

use strict;
use warnings;
use Getopt::Long;
use Pod::Usage;

#Usage part

my $fasta_split_VER = '0.01';
my ($opt_help, $opt_man, $opt_versions, $opt_name, 
  $outfile, $infile, $number_of_chunks, $chunk_name);

GetOptions (
  'help'     => \$opt_help,
  'man'      => \$opt_man,
  'versions' => \$opt_versions,
  'name'     => \$opt_name,
  'in=s'      => \$infile,
  'chnb=i'      => \$number_of_chunks,
  'chnm=s'      => \$chunk_name,
) or pod2usage(-verbose => 1) && exit;


pod2usage(-verbose => 1) && exit if defined $opt_help;
pod2usage(-verbose => 2) && exit if defined $opt_man;
pod2usage(-verbose => 99, -sections => [qw(NAME SYNOPSIS)]) && exit if
+ defined $opt_name;


if(defined $opt_versions){
    print
      "\nModules, Perl, OS, Program info:\n",
      "  Pod::Usage            $Pod::Usage::VERSION\n",
      "  Getopt::Long          $Getopt::Long::VERSION\n",
      "  strict                $strict::VERSION\n",
      "  Perl                  $]\n",
      "  OS                    $^O\n",
      "  fasta_split.pl        $fasta_split_VER\n",
      "  $0\n",
      "\n\n" and exit;
}

#end Usage part

#define number of chunks and chunk name
open(my $instream, "<", $infile) or die ("error opening input file $in
+file: $!");
...
} #end second part

exit;

=head1 NAME

 fasta_split.pl

=head1 SYNOPSIS

 perl fasta_split.pl --in=input_file --chnb=number_of_chunks --chnm=ch
+unk_name

=head1 DESCRIPTION

 Split fasta file into number of chunks. Chunks get short name + numbe
+r.
 
 You need to provide input file, number of chunks and chunk name.

 For help write:
 perl fasta_split.pl --help
 perl fasta_split.pl --man
   

=head1 ARGUMENTS

 --help      print Options and Arguments instead of splitting fasta
 --man       print complete man page instead of splitting fasta

=head1 OPTIONS

 --versions   print Modules, Perl, OS, Program info
 --name       print name of the script and synopsis
 --in=input   name of the input file
 --chnb=50    number of chunks needed
 --chnm=hx    name of the chunks

=head1 TESTED

 Modules, Perl, OS, Program info:
 Pod::Usage            1.51
 Getopt::Long          2.39
 strict                1.07
 Perl                  5.016001
 OS                    MSWin32
 fasta_split.pl        0.01
 
=head1 BUGS
 F:\luka_blast\in>perl fasta_split17.pl
 Use of uninitialized value $infile in open at fasta_split17.pl line 4
+6.
 Use of uninitialized value $infile in concatenation (.) or string at 
+fasta_split17.pl line 46.
 error opening input file : No such file or directory at fasta_split17
+.pl line 46.


=head1 TODO

 I have no idea.
   

=head1 UPDATES

 12.02.2014.
 Initial working code

=head1 EXAMPLE
 F:\luka_blast\in>perl fasta_split17.pl --in=hu_ex_cl.txt --chnm=jura 
+--chnb=50
 Num of seq: 22106
 Num of chunks: 50
 Num of seq in chunk: 442
 Num of seq left without chunk: 6
 File: jura1
 ...
 File: jura50
 Last file appended:jura50
=cut
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