COMMAND1  (1)
    VALUE1
    VALUE2
    VALUE3
    ...
  COMMAND2  (2)
    VALUE1
    VALUE2
    ...
  COMMAND3  (3)
    VALUE1
    ...

##</code><code>##

use strict;
use warnings;
use Data::Dumper;

# define command enums
my @commands = qw/ COMMAND1 COMMAND2 COMMAND3 /;
my @parameters = (              
        [qw/ VAR1 VAR2 VAR3 /], # variables for COMMAND1
        [qw/ VAR1 VAR2 /],      # variables for COMMAND2
        [qw/ VAR1 /],           # variables for COMMAND3
    );

# define possible input
my %input;
@input{@commands} = @parameters;

# debug
# print "Possible Inputs => ", Dumper(\%input);

my ($command, $parameters) = __ParseInputFromVB();
die "Unknown command $ARGV[0]" if ! defined $command;
die "Incorrect parameters for $command" if ! defined $parameters;

# debug
print "Want to process: $command => ", Dumper($parameters);

# dispatch the command
__PACKAGE__->$command(@{$parameters});



# returns the name of the command and parameters
sub __ParseInputFromVB
{
    return () if $#ARGV < 0;  # no command specified

    return () if $ARGV[0] !~ /^\d+$/;   # command is a number

    my $command = $commands[$ARGV[0] - 1];

    # check if the command is defined or not
    return () if ! defined $input{$command};

    # check for required parameters
    my $arglist = $input{$command};
    return ($command, undef) if $#$arglist != $#ARGV-1;

    # if want a hash of parameters
    # my %param;
    # @param{@$arglist} = @ARGV[1..$#ARGV];
    # return ($command, \%param);

    # if a list of parameters
    my @param = @ARGV[1..$#ARGV];
    return ($command, \@param);
}

# handlers for commands
sub COMMAND1
{
    my (undef, $var1, $var2, $var3) = @_;
    # ....
    print "process command 1, param: $var1, $var2, $var3\n";
}

sub COMMAND2
{
    my (undef, $var1, $var2) = @_;
    # ....
    print "process command 2, param: $var1, $var2\n";
}

sub COMMAND3
{
    my (undef, $var1) = @_;
    # ....
    print "process command 3, param: $var1\n";
}

##</code><code>##

C:> perl p110.pl 1 a b c
Want to process: COMMAND1 => $VAR1 = [
          'a',
          'b',
          'c'
        ];
process command 1, param: a, b, c

C:> perl p110.pl 1 a b
Incorrect parameters for COMMAND1 at p110.pl line 22.

C:> perl p110.pl X a b
Unknown command X at p110.pl line 21.