> I've worked with many languages both professionally and (very) casually, probably over a dozen. I only put the ones I have mastered on my resume.
And that is excellent and I would consider that perfectly normal and rational behavior. You have more than one. You took the time to explore. It's a field of constant problem solving and lack of exploration of solutions is something that sticks out as a giant red flag because of that.
More experience is definitely better. If I were hiring for a particular language I'd certainly want more than a weekend's experience, but some experience is still better than no experience.
At my last job we interviewed a guy who was about 5 years out of college and had been working in a .NET shop the entire time. He was applying for a ruby position and his only experience was spending a couple of weeks in his spare time building a Rails site. From that minimal experience, we were able to get him to explain why he decided to pursue it, what he liked about it, what problems he was trying to solve, what weaknesses he was trying to overcome that he was seeing in .NET, etc.
Despite the lack of language experience, we hired him based on the "geek gene" that clearly showed problem solving skills and desire to learn. The guy was absolutely rock solid and became one of our most valuable team members within about 2 months time. I believe he's the CTO of a funded startup now if I remember correctly.
If he'd had only Rails and I'd asked him about what weaknesses he saw with the stack...my very next question would have been what he tried to do to overcome those weaknesses. Maybe he answers about what other things he tried within the stack, caching techniques, using jRuby, refactoring in certain ways, etc and as long as that could be articulated it would generally be okay. In general though, seeing how other languages handle the same problem is going to be perfectly normal part of the process...which should lead to having more than one language on the resume.