Again I recommend reading perlipc, as hossman has seconded. The other things he also suggests are good places to start.

As for capturing all signals you might look at sigtrap. Or you could do the following:

$SIG{$_} = \&handler for keys %SIG;
[download]

Note that will also call handler when you die or warn.

--
perl -pe "s/\b;([mnst])/'\1/mg"