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mediawiki.jqueryMsg can not handle external links with dollar signs in the URL.  However, those are valid.  See bug 188 and https://en.wikipedia.org/wiki/MediaWiki:Version-entrypoints-articlepath .

External links are defined as:

sequence(openExtlink, nonWhitespaceExpression, whitespace, expression, closeExtlink)

So the URL must go in nonWhitespaceExpression.  That in turn is:

choice(template, link, extLinkParam, extlink, replacement, literalWithoutSpace)

This seems overly broad, since I don't think we allow nested external links... However, the one that should match is literalWithoutSpace.

That is nOrMore( 1, escapedOrLiteralWithoutSpace )

escapedOrLiteralWithoutSpace is:

choice(escapedLiteral, regularLiteralWithoutSpace)

So I think the root problem is regularLiteralWithoutSpace, which is:

makeRegexParser(/^[^{}\[\]$\s]/);

I think this should allow $, which means removing it from the negative character class.