I've uploaded the initial release of Tie::Constrained (v0.03) to CPAN. Many thanks to diotalevi for his interest and assistance in preparing the package.

Tie::Constrained gives the means to monitor, validate or filter any changes your program makes to a variable. It can automatically validate and untaint data from untrusted sources upon assignment to the tied variable.

This module first saw light here on perlmonks, in To Validate Data In Lvalue Subs, and later in Tie Me Up, Tie Me Down.