A localizing of blocking/unblocking through hash is super idea :)
I can block / unblock signal and can do nested blocks as i think (but about this no documentation - about nested blocks)
The 'local' keyword is simple tool for saving / restoring bit mask of signals.
This module will be useful everybody who makes daemon programs. System calls can be easy interrupted by harmless signals - for example flock, sysread and syswrite, DB connections (DBI functions can lose connect to DB during transaction after TERM signal but you might want to catch it yourself) can be interrupted by SIGCHLD signal if you do wait() yourself. And there many other examples. This module will help to wrap these code blocks by this module.