Odd. I got it of cpan.. guess was a while ago

I know it was abstracted heavily from Unix::ConfigFile That may have smothing for you..

Looks like the Unix::PasswdFile might handle the shadow as well..
also CfgTie::TieShadow looks like it could make it easier.

as well the author is of Unix::ShadowFile is: Steve Snodgrass, ssnodgra-AT-fore.com
you can try him. if all else fails email me and i will send you the .pm i got