#do{$data = $data . $_ } while (<DATA>); #gives a uninitialized value in concatenation

##</code><code>##

my $data;
while (<DATA>) { $data .= $_ }

##</code><code>##

$ perl -we 'my $foo; $foo = $foo . "foo"'    # no warning

##</code><code>##

$ perl -we 'my $foo; my $bar = $foo . "foo"'
Use of uninitialized value $foo in concatenation (.) or string at -e line 1.