You're probably right, but I prefer defensive programming. In production code, I hate such assumptations, as there is always a chance that they will break in strange spots. Here, maybe a network drive on windows with double back slash like \\server or so might be nasty, or maybe the path might be in future something like ftp://home/temp/login. Maybe some internal stuff allows creating hidden anything with [/\\] inside, like perl allows us to create a sub "Hi with spaces inside" if we just manipulate the symbol table. I don't know for sure and won't know if something goes wrong why.

So I try to advocate using modules that do exactly this job like File::Basename or Path::Tiny. At least, if those are much used modules, there is a lesser chance that things might go wrong.

Of course, if I just write a snippet, I'd split m:[/\\]:, ... in a heart beat, also. No need to check a module doc if all you want is a short script that won't be used by other (persons/modules/programs).