# Use something more sophisticated which escapes properly.
sub quote { qq!"$_[0]"! }

my ($x, $y, $z) = qw/ X Y Z /;
my $str = 'Foo $x bar $y baz $z';
print $str;              # Foo $x bar $y baz $z
print quote($str);       # "Foo $x bar $y baz $z"
print eval quote(str);   # Foo X bar Y baz Z