you can't switch "exit" handlers midstream, and you can't unregister END{} blocks,

But you can enable or disable code in the END blocks by using flag variables:

>cat demo.pl
#!/usr/bin/perl

use v5.12;
use warnings;

our $endFlag;

END {
        if ($endFlag) {
                say "End flag is set, have to so some cleanup";
                say "Wash, rinse, repeat" for 1..5;
        } else {
                say "Nothing to do";
        }
}

$endFlag = $ARGV[0];

say "How will this end?";
>perl demo.pl 0
How will this end?
Nothing to do
>perl demo.pl 1
How will this end?
End flag is set, have to so some cleanup
Wash, rinse, repeat
Wash, rinse, repeat
Wash, rinse, repeat
Wash, rinse, repeat
Wash, rinse, repeat
>
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Alexander