BEGIN {
    our $DEBUG = 1;
}

##</code><code>##

my $DEBUG = $main::DEBUG;
<code>
<i>However</i>, $DEBUG was then not available <i>within</i> main!
<br><br>
I don't know the reason for that, but I resolved it by doing this further down in main:
<code>
my $DEBUG = $main::DEBUG;