MacOSX directory syntax

I wrote a simple perl script on macOS9.2 and want to move to an OSX box.
When I run it on the OSX box, my path syntax is not working. Is the path
syntax for OSX different than OS9?

my $files_to_move = ':In'; #top level folder for search

In this line, ":In" does not resolve. The "In" directory is in the same
directory as the perl script.

Thx.

--> [groundZERØ]
--> [t:o:m:c:a:r:r]
--> [[email protected]]
--> [847:757:4188]