This question pops up a lot, and time and time again, people misunderstand the question and reply as Joey the Saint did. See, for example, this recent thread in comp.lang.moderated. Especially the standpoint of M.J.Dominus is interesting. It brings up a point I have wondered myself a lot: since Perl does interpolation, very well, why is it not available as a user accessible function?

Now, the solutions proposed there are pretty much the same poorish solutions as proposed here: escape the quotes, put quotes around it, and eval. Or search for /\$\w+/ and replace it with the value you want it to have, perhaps using symbolic references (!).

A potentially better, and likely safer, solution might be to treat the replacement as a template, and use one of the several templating modules to process it, and incorporate the result that comes out of that, into the substitution.