I just installed media-tv/ivtv and I wanted to use ptune.pl for tuning the tunner. I was surprised that media-tv/ivtv didn't installed all necessary modules for perl even if it installed perl script into system. I propose to add USE flag "ptune" and if this flag is set, install also the perl modules (dev-perl/Video-Frequencies, dev-perl/Video-ivtv, dev-perl/Config-IniFiles, perl-core/Getopt-Long, dev-perl/perl-tk).
Well, you didn't say what version of media-tv/ivtv you used... but I just added 1.0.3-r2. I believe ptune was only recently re-integrated back in. It used to be it's own package called ivtv-ptune. Give it a try, I personally don't use ptune.