Looks like it. HTMLhelp.com doesn't mention a separate parameter for name=value, only name.x and name.y. Neither does the official HTML spec.

It looks like you'll have to find another way, like making your page number part of the name, such as

<INPUT type="image" name="page23" src="...">
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A grep through all params with a name matching /^page(\d+)\.x$/ will then find your page number.

($param) = grep /^page\d+\.x$/, $cgi->param;
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Or, using map, and the fact that a regex that doesn't match returns an empty list, and a list of captured matches if it does, that can even become:

($page) = map /^page(\d+)\.x$/, $cgi->param;
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That doesn't look half bad to me.