kill INT => $pid;
# which is the same as
kill 'INT', $pid;

##</code><code>##

$SIG{INT} = sub { 
 # code executed on 'INT' signal here
}; # <-- that semicolon isn't optional

##</code><code>##

{
  my $stop = 0;
  local $SIG{INT} = sub { $stop++ }; 
  while (!$stop) {
    # the loop continues until it's left with an explict
    # last, or until the process recieves SIGINT.
  }
}
# our old SIGINT handle is restored here, because we
# left the old block.