Given this snippet:

$_ = `cd`; chomp; print;
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I gather you are not using any sort of unix-like system, or any unix-style version of the "cd" command ported for use on a windows system.

In any flavor of unix, a bare "cd" command sets the CWD to your home directory (typically "/home/yourname"), and produces no output on stdout. So doing this within backticks in a perl script will set $_ to an empty string, and have no effect on the script's behavior in any way -- except for using up the time it takes to spawn a shell process, do a useless "cd" command in that process, and then shut down the shell.

Definitely go with the Cwd module. It's part of the core distribution, and provides uniform behavior on all platforms.