IO::String will let you do in-memory, in-core file operations, a "simulated file":

#!/usr/bin/perl

use strict;
use warnings;
use IO::String;

my $str = <<EOT;

Four score and seven years ago our fathers
brought forth on this continent, 
a new nation, conceived in Liberty, and dedicated 
to the proposition that all men are created equal.
EOT

my $io = IO::String->new($str);
$io->open('STDOUT');
my @lines = <$io>;
$io->getline;
my $buf = "";
read($io, $buf, 100);
select $io;
print STDOUT "$str\n";
$io->close('STDOUT');
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