Looks like there were changes in the latest version that may fix signature problems in the previous version (i.e., try upgrading?):
Perltidy Change Log
2016 03 02
- RT #112534. Corrected a minor problem in which an unwanted new
was placed before the closing brace of an anonymous sub with
a signature, if it was in a list. Thanks to Dmytro Zagashev.
- Corrected a minor problem in which occasional extra indentatio
given to the closing brace of an anonymous sub in a list when
parameter was set.
2016 03 01
- RT #104427. Added support for signatures.