I would use the following code:

#! /usr/bin/perl

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

my $file = './test.txt';
my @array;

{
  local $/ = "\nlevel";
  open(FILE,"<$file") or die $!;
  while(my $entry = <FILE>){
    chomp $entry;
    $entry = 'level'.$entry unless($entry =~ /^level/);
    push(@array,$entry);
  }
}

print Dumper(\@array);
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