#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my $file = '/path/to/file.txt';

my @array;

{
    local $/ = "\nMessage:";
    open my $fh, '<', $file or die $!;
    while( my $entry = <$fh> ){
        chomp $entry;
        $entry = "Message:".$entry unless $entry =~ /^Message/;
        push @array,$entry;
    }
    close $fh;
}

print Dumper(\@array);