$ perlcritic your-script.pl
Loop iterator is not lexical at line 13, column 1.  See page 108 of PBP.  (Severity: 5)
Bareword file handle opened at line 15, column 1.  See pages 202,204 of PBP.  (Severity: 5)
Two-argument "open" used at line 15, column 1.  See page 207 of PBP.  (Severity: 5)