#!/usr/bin/perl -w
use strict;
#-----------------------
package StringHandle;
use overload 
    '<>' => sub {
        return shift @{$_[0]};
    };
    
sub new {
    my $class = shift;
	return bless [split /^/m, $_[0]], $class;
}

sub close {
    # does nothing. Just to emulate FileHandle
};
#-----------------------

package main;
use FileHandle;

my $param = shift;
my $text  = undef;

if ($param) {
    $text = new FileHandle $param 
        || die "can't open $param\n";
}
else {
	$text = new StringHandle "aaa\nbbb\nccc\nddd\n"
		|| die "can't create new handle\n";
}

print while <$text>; # reads from either a file or a string

$text->close;