(CORE::exit IIRC)

Use CORE::GLOBAL::exit() to override — CORE::exit() is the original exit builtin that you'd typically call from within your redefined exit routine...

Update: an example:

#!/usr/bin/perl

BEGIN {
    *CORE::GLOBAL::exit = sub (;$) {
        print STDERR "in overridden exit(): @_\n";
        CORE::exit(88);
    };
}

exit 99;
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