while (<DATA>) {
   chomp;
   $_ =~ s/^&(\w+)([\(\)]*)/$1()/;
   print "$_\n";
}

__DATA__
&foobar
&foobar()
foobar()
&foobar("asdf")

##</code><code>##

foobar()
foobar()
foobar()
foobar()"asdf")

##</code><code>##

while (<DATA>) {
   chomp;
   $_ =~ s/^(&)(\w+(\([\"\'\$\w]*\))?)(\(\))$/$2()/;
   print "$_\n";
}

##</code><code>##

&foobar
foobar()
foobar()
&foobar("asdf")