I was just hired into this exact scenario. I am a C++ and Java developer and had never touched Perl until my current job. The things that took some time to get used too were the idiosyncratic Perl syntax choices [$_], $this = that unless ... , and seeing the forest for the trees (anything containing /^#+\d/ elements). Other things were just a result of the programming house I work in [confusing OO statements, $self, and putting 1; at the end of module files].
Now that I have been here a while, I see the elements of style that Perl has given me even in my non-work projects. You approach tasks, especially data massaging, differently and it feels like a real solid tool in my toolbox.
All that being said, I was handed a codebase of around 35,000 lines, the camel book and told I could not use CPAN. It has been a productive six months. ^^
