#!/usr/bin/perl

use strict;
use warnings;

my($bad)='/this/path/does/not/exist';
die "$bad exists, but must not\n" if -f $bad;

my($yes1)=(defined $bad and -f $bad); #2nd parens seem unnecessary,
die "yes1=$yes1\n" if $yes1;          #but does not die here; good

my($yes2)=defined $bad and -f $bad;   #2nd parens removed,
die "yes2=$yes2\n" if $yes2;          #but dies here; why?