Updated: to include the cut_out.txt file.

#!/usr/bin/perl -w
use strict;
use IO::All;

my @cut_out = io("cut_out.txt")->slurp;
my @lines = io('original.txt')->slurp;

my $total_lines = 0;
$total_lines += $_ foreach @cut_out;

for (my $i = 0; $i <= ($total_lines - 1); $i++ ) {
    $i <= $cut_out[0] - 1 ? 
    io("1.out.test.txt")->append($lines[$i]) :
    io("2.out.test.txt")->append($lines[$i])
}
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