Can you tell me please what should i change or add in this code? Where do i have typo?

No, the code you posted doesn't exibit the problem, doesn't show the error message, so there is nothing to change in the code you posted to resolve some error message you haven't copy/pasted.

But if you add  use diagnostics; at the top of your code, it will tell you what type of situation causes the error message and how to resolve it.

A tutorial explaining what strict is all about Read this if you want to cut your development time in half!

Tutorials on understanding perl variable rules ( and why strict helps with that) : Variable Scoping in Perl: the basics, Coping with Scoping , Mini-Tutorial: Perl's Memory Management, Lexical scoping like a fox, Read this if you want to cut your development time in half!