While I don't know of any perl-centric solutions to the problem of DTMF recognition beyond using PDL to implement a Fast Fourier Transform of some sort, to determine frequency and mapping that to a list of frequencies/dtmf tones...
There is a library called 'amTapi', that's fully TAPI compliant. amTapi purports to support DTMF detection and playback of wave files to telephony devices (among other features). It's written in C++, but you could (most likely) easily interface to it using XS. If you do happen make an XS interface, please share! =)

At any rate, since you're on windows, you should *definately* read up on TAPI which is the standard API for telephony devices under Win32.