would you say that Perl is not a strong type language since we do not need to define the type of the variable?

Actually, you must define the type of the variable in Perl by using the right sigil. It's a question of specificity.

Questions about whether a language is strongly typed or not don't lead to anything productive. It's usually used to apply against preconceptions about code robustness, code size, coding speed, etc. Those are definitely interesting areas of study. Whether a language is strongly typed or not isn't. In short, your question suffers from the XY Problem.

I recommend that you read the results of Dominus's attempt to define "strongly typed".

Dynamic programming language - execute at runtime many common behaviors that other languages might perform during compilation

Given how common dynamic programming languages have become, your definition doesn't match any languages. Your definition is a contradiction.