Re: what is this error means Use of uninitialized value $. in concatenation (.) or string

[Corion]

$. is a variable in Perl. See perlvar.

You are interpolating this variable in the string $.ajax(.... I recommend putting Javascript in a separate file and reading it from Perl, or alternatively using a non-interpolating here-document:

print <<'EOF';
  This costs many $$$
EOF