#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

{
    open(my $first_fh, "<", "file1.txt");
    my @file1_lines = <$first_fh>;
}

{
    open(my $second_fh, "<", "file2.txt");

    while (my $line = <$second_fh>) {
        my @data = my_sub($first_fh, $line);
    }
}

sub my_sub { 1 }

##</code><code>##

Global symbol "$first_fh" requires explicit package name ... line 16.
Execution ... aborted due to compilation errors.

##</code><code>##

Can't open 'file1.txt' for reading: 'No such file or directory' ... line 8