Wrong. Perl false is !1. (PL_sv_no in the C source) It's a dualvar with a string value of "" and a numerical value of 0.
See: Re^4: m//g behaves strange... (!1). And this snippet:
$ perl -lwe 'for (qw/undef 0 "" !1 1==2/) { print "\n\$a = eval $_;";
+$a = eval $_; print "$_:\t|$a|", 1+$a; }'
$a = eval undef;
Use of uninitialized value in concatenation (.) or string at -e line 1
+.
Use of uninitialized value in addition (+) at -e line 1.
undef: ||1
$a = eval 0;
0: |0|1
$a = eval "";
Argument "" isn't numeric in addition (+) at -e line 1.
"": ||1
$a = eval !1;
!1: ||1
$a = eval 1==2;
1==2: ||1
