#!/usr/bin/perl -w
use strict;

my $logfile = "/var/log/whatever.log";
my $verbose = 0;

parseArgs($#ARGV + 1, @ARGV);

#
# ... do stuff with the logfile ...
#

# subroutine parseArgs
sub parseArgs {
   my ($argc, @argv) = @_;
   my $need_help = 0;

   # is mandatory to receive comand args?
   usage() if ( $argc == 0 );

   for ( my $i=0; $i < $argc; $i++ ) {
      foreach ($argv[$i]) {
         if ( /^-logfile$|^-l$/ ) {
            if ( $argv[$i + 1] ) { 
               #here you must do, if you want, some checks
               #before asing nothing ...
               $logfile = $argv[++$i];
            } else {
               #complain!
               $needs_help = 1;
            }
         } elsif (/^-v$|^--verbose$/) {
            $verbose = 1;
         } elsif (/^-h$|^--help$) {
               $needs_help = 1;
         } else {
            print "Command argument ", 
                  ($argv[$i]),
                  " is not valid\n");
            $needs_help = 1;
         }
      }
   }
   usage() if ( $needs_help );
}

sub usage {
   print <<EOF
usage: program [-l logfile] [-v] [-h]
 blablabla ....
EOF
   exit 0;
}