Venerable ones,
The question is "what to do about those alarm timeouts we've been using pre-5.8?" For syscalls in 5.8, the opcode/XS code has to finish/raise a signal/time out before returning to our code, rendering our signal timeout setting ineffectual.
Illustration:

#!/usr/bin/perl -w
use strict;
use Time::HiRes qw( gettimeofday tv_interval );
print "$]\n";
my $elapsed = 0;
my $start_time = [gettimeofday];
eval {
    local $SIG{ALRM} = sub {
        $elapsed = tv_interval( $start_time );
        warn "alarm-timeout signal";
        die;
    };
    alarm(1);
    `ls -R / 2>/dev/null`;
    alarm(0);
};
print "$@"  if $@;
print "$elapsed\n";
[download]

Output on 5.6:

5.006
alarm-timeout signal at /home/jbho/bin/test_SIGALRM.pl line 15.
Died at /home/jbho/bin/test_SIGALRM.pl line 16.
0.999504
[download]

Output on 5.8:

5.008
alarm-timeout signal at /home/jbho/bin/test_SIGALRM.pl line 15.
Died at /home/jbho/bin/test_SIGALRM.pl line 16.
109.948451
[download]

Suggestion put out by member(s) of the community:

use POSIX ':signal_h';
my $alarm = 0;
sigaction SIGALRM, new POSIX::SigAction sub { $alarm = 1 }
    or die "Error setting SIGALRM handler: $!\n";
[download]

This solution would bypass the perl implementation for setting the signal.
What say you?

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