multiple + other -- most of those would influence whether or not I use it. And a few other influencing params:

• it works for me
• it's the only interface (or most-readily available interface) for an external library
• using the approximate solution found in the CPAN module was easier than coding a whole exact solution by myself
• using the premade solution had better edge-case coverage than what I came up with
• which criteria was used depended on the exact specifications for the code being developed
• it works on Windows with Strawberry Perl, not just on linux
  → aka "good cross-platform compatibility"
• it works on an ancient machine with perl v5.8 (or preferably v5.6)

and though this hasn't influenced me yet, I know it does some monks:

• it's small enough to fit on (insert favorite small embedded system with a tiny perl here)