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 +line 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 +n was given to the closing brace of an anonymous sub in a list when +the -lp parameter was set. 2016 03 01 - RT #104427. Added support for signatures.