You'll find documentation at perlman:perlvar; search for '%SIG'. Here's some example code.

# Handles when we exit with a 'die "foo"...'
sub die_handler {
    my ($msg) = @_;
    shutdown_now("Died; $msg");
}

$SIG{__DIE__} = \&die_handler;
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You can also install signal handlers on POSIX-compliant systems using sigaction(); see POSIX for details.

stephen