Firstly, sorry for mis-spelling your name.

I also apologies for misunderstanding your intent. In the context of the thread, I looked at what FreezeThaw did, and couldn't see the difference between what it did in cmpStr($x,$y) and do{no warnings; $x eq $y). However, as I finally got FreezeThaw.pm installed on my system (actually just copied in as the install mechanism gave me inordanant troubles), I realise that it does more as my test script below shows.

#! perl -sw
use strict;
use FreezeThaw qw(cmpStr freeze);

sub asStr {
    return 'undef' if !defined $_[0];
    return "''" if $_[0] eq '';
    return '0' if $_[0] == 0;
    "$_[0]";
}

my @x = (0,1,'',undef);
my @y = (0,1,'',undef);

print '                  {$^W=0; ($x eq $y)', "\t", '!cmpStr($x,$y)', 
+$/;
for my $x (@x) {
    for my $y (@y) {
        printf '%5s -v- %5s :', asStr($x), asStr($y);

        print "\t", do{local $^W=0;($x eq $y) ? 'Same' : 'Diff';};

        print "\t\t",!cmpStr($x,$y) ? 'Same' : 'Diff', $/;
    }
}
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Giving

C:\test>test
                  {$^W=0; ($x eq $y)    !cmpStr($x,$y)
     0 -v-     0 :       Same            Same
     0 -v-     1 :       Diff            Diff
     0 -v-    '' :       Diff            Diff
     0 -v- undef :       Diff            Diff
     1 -v-     0 :       Diff            Diff
     1 -v-     1 :       Same            Same
     1 -v-    '' :       Diff            Diff
     1 -v- undef :       Diff            Diff
    '' -v-     0 :       Diff            Diff
    '' -v-     1 :       Diff            Diff
    '' -v-    '' :       Same            Same
    '' -v- undef :       Same            Diff # Here!
undef -v-     0 :       Diff            Diff
undef -v-     1 :       Diff            Diff
undef -v-    '' :       Same            Diff # Here!
undef -v- undef :       Same            Same

 1:13:29.67 C:\test>
[download]