I'm not sure if this is a question or a meditation really.

I asked a recent question about a problem with open3(). It turned out that the problem was really with my use of local signal handlers.

The following code works with 5.10.1 but not with 5.14.2:

#!/usr/bin/perl
use strict;
use warnings;
print "starting pid=$$\n";
my $I = 0;
{
    my $pid = 0;
    sub handler {
        my $sig = shift;
        $I += 1;
        print "caught $sig\n";
        local $SIG{$sig}  = 'IGNORE';  # doesn't work with local!!
        kill($sig, -$$);
        print "end of handler\n";
    }   
    local $SIG{INT}  = \&handler;
    kill('INT', $$);
}
print "ending I=$I\n";
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With 5.10.1, it calls handler() twice and then exits with I=2; with 5.14.2 it calls the handler many times before crashing with a segfault.

Removing the local from the inner $SIG{$sig} allows it to work with 5.14.2, which makes sense if I'm right in thinking that that command changes the immediately-containing signal handler, and not the global one.

So my question is: Since this can break existing (poorly written) code, is this a known effect, and if so, is it documented?

cheers

Chris