Maybe you want to show us your code, the input, and what error(s) you get when the two come together?

Maybe you want to read perlop, especially on the eq operator for string comparison.

Alternatively, read perlre, about regular expressions that could match such a string.

Maybe you just want to play it safe and HTML-escape all parameters before interpolating them into any HTML output, as you should, potentially by using HTML::Entities?