Turn that around and ask what thing can only be done one way (if at all) in some languages, but one or more ways in Perl. Classes/objects come to mind immediately. Functional programming is another.

For other things, while there may not be only one way to do it in other languages, Perl offers many more options. For that, loops and loop control comes to mind, particularly postfix modifiers and next, last, map, grep, etc. All the array modifiers might be in that camp, too.

In a more abstract sense, subroutine argument passing and argument type validation is something that gets done lots of different ways in Perl, where in some other languages that is never even a question the programmer has to consider.

Some of these are exactly the kinds of things that Perl 6 is trying to define in a more standard way.