Eureka!

Look at this code -- it works without threads! So, threads aren't the magic here.

#!perl -w
use strict;

print "Enter CTRL-C to end input\n";
$SIG{INT} = 'IGNORE';
my @rv = <STDIN>; 
eval q/$SIG{INT} = 'DEFAULT'/;
chomp @rv;
print "Enter CTRL-C to exit\n";
while ( 1 )
{
   local($") = ', ';
   print "You entered: @rv\n";
   sleep(1);
}
[download]

Is another Perl interpreter instance being launched to handle that eval()? Or is the first instance looking for all of the places that twiddle %SIG, and evaluating them upfront? Perhaps there are only a handful of things (like spawning a thread or calling eval()) can get the Perl interpreter to push the state of %SIG down into the operating system?

Thoughts on just what the mechanics are behind this behavior?