First of all, add use strict; to the top of your script. This will enable Perl to warn you that it finds an array (@jnpodb).

Then, read perlop (and perlre) on how to escape things in regular expressions and strings.

You need to escape the @ by quoting it with a backslash:

\@jnpodb
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@jnpodb is seen by Perl to be an array. And the righthand side of a substitution is subject to double-quote-like interpolation. Therefore, Perl interpolates the contents of @jnpodb into your replacement string. Since that variable exists nowhere else, it's empty, and consequently what gets interpolated is the empty list which is upgraded to an empty string.

If use warnings were in use, you would get a warning about interpolating an undefined value. And if use strict were in use, you would get a fatal compiletime error stating that @jnpodb wasn't pre-declared in scope. More clues about errors is better than fewer clues, so always use strict and warnings.

And as it goes with double-quotish interpolation, you just need to escape the sigil. Thus, this works:

There is nothing wrong with cross-posting, but it is considered polite to inform the reader to avoid duplication of work at various ends of the Internet.