my $string .= 'appended stuff' if ($conditional1);

##</code><code>##

my $string = $string . 'appended stuff' if ($conditional1);
#which is basically (or is it not and that's the problem?):
my $string = undef . 'appended stuff' if ($conditional1);

##</code><code>##

my $conditional1 = 0;
my $string = 'blah' if $conditional1;
# $string is undef