my $oldhandler = $SIG{SOMETHING};
$SIG{SOMETHING} = sub {
 # do whatever 
 if ($oldhandler) {
    $oldhandler->();
 }
};

[download]
Notes:

1. this assumes that the other code does something like this as well, or that your handler is installed after the old one. See for instance my pretty simple CGI::HTMLError.

2. some kinds of signals (like SIGCHLD) are more complicated than this and may need special care.

"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: Chaining/Stacking $SIG{__WARN__} by Joost
in thread Chaining/Stacking $SIG{__WARN__} by Anonymous Monk

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