Use IO::Scalar to read data chunks line by line

splitterify.pl

#!/usr/bin/env perl

use strict;
use warnings;
use 5.010;
use Carp;
use autodie;
use utf8;

use IO::Scalar;

my @chunks = (
    qq{I'm a chunk! but I'm not a complete line},
    qq{ ... the second chunk completes this line\nand adds another line\nand starts a third},
    qq{ ... this is my EOF});

my $buffer = '';

my $sh = IO::Scalar->new(\$buffer);

while (my $chunk = shift @chunks) {

    $buffer .= $chunk;

    while (my $line = $sh->getline) {
        # remove what we just read from the buffer
        substr($buffer, 0, length($line), '');
        $sh->seek(0, 0);
        unless (chomp $line) {
            say "partial line: $line";
            $buffer = $line . $buffer;
            last; # and wait for the next chunk
        }
        say "got a complete line: $line";
    }

}

say "this is the remainder: " . $sh->getline;