in all honesty, my brain gives up on at least three things - quantum physics, Trump-supporters, and type-globs...

Thanks for making me laugh. :) I'm relieved you didn't mention your brain giving up on use strict, use warnings and lexical variables. You really need to embrace all three. To give a simple example why, notice that this code:

use strict;
use warnings;
sub fred {
    my $fname = 'f.tmp';
    open( FH, '<', $fname ) or die "error: open '$fname': $!";
    print "file '$fname' opened ok\n";
    # ... process file here
    die "oops";   # if something went wrong
    close(FH);
}
eval { fred() };
if ($@) { print "died: $@\n" }
# oops, handle FH is still open if an exception was thrown.
my $line = <FH>;
print "oops, FH is still open:$line\n";
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is not exception-safe because the ugly global file handle FH is not closed when die is called.

A simple remedy, as noted at Exceptions and Error Handling References, is to replace the ugly global FH with a lexical file handle my $fh, which is auto-closed at end of scope (RAII):

use strict;
use warnings;
sub fred {
    my $fname = 'f.tmp';
    open( my $fh, '<', $fname ) or die "error: open '$fname': $!";
    print "file '$fname' opened ok\n";
    # ... process file here
    die "oops";   # if something went wrong
    close($fh);
}
eval { fred() };
if ($@) { print "died: $@\n" }
print "ok, \$fh is auto-closed when sub fred exits (normally or via di
+e)\n";
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