#!/usr/bin/perl
use strict;
use warnings;
use Getopt::Std;

my $opt = {};
Get_Args( $opt );

my $fh;
if ( $opt->{o} ) {
    open ( $fh, '>', $opt->{o} ) or die "Unable to open $opt->{o} for writing : $!";
}
else {
    open ( $fh, '>&', *STDOUT ) or die "Unable to dup STDOUT : $!";
}
select $fh;
$| = 1;

print "foo bar\n";

sub Get_Args {
    my $opt = shift;
    my $Usage = qq{Usage: $0 [options]
        -h : This help message.
        -o : Output file - STDOUT by default
    } . "\n";

    getopts( 'ho:' , $opt ) or die $Usage;
    die $Usage if $opt->{h};
}