my $foo;
my $bar = '043';

my $s1 = '$foo = $bar';
print "s1: ", $s1, "\n";
print "eval=", eval($s1)//$@, ", \$foo=$foo\n";

my $s2 = "\$foo = $bar"; # same as '$foo = '.$bar
print "s2: ", $s2, "\n";
print "eval=", eval($s2)//$@, ", \$foo=$foo\n";

__END__

s1: $foo = $bar
eval=043, $foo=043
s2: $foo = 043
eval=35, $foo=35