Documentation says:
splitpath
Splits a path in to volume, directory, and filename portions. On systems with no concept of volume, returns '' for volume.
- ($volume,$directories,$file) = File::Spec->splitpath( $path );
- ($volume,$directories,$file) = File::Spec->splitpath( $path, $no_file );
For systems with no syntax differentiating filenames from directories, assumes that the last file is a path unless $no_file is true or a
trailing separator or /. or /.. is present. On Unix, this means that $no_file true makes this return ( '', $path, '' ).
The directory portion may or may not be returned with a trailing '/'.
The results can be passed to catpath() to get back a path equivalent to (usually identical to) the original path.
So splitpath returns a tuple and the third element of the tuple is just the filename, as opposed to the entire file path. Presumably bumpFile contains the full path of the file not just a filename. They're basically just trying to change the working directory and to work no matter what was stored in bumpfile (i.e. an entire path, a file, a relative file path, etc). The code will work if you pass in "../../twizzlers.txt" or "./twizzlers.txt" and maybe just "twizzlers.txt".
The system command creates a new file which is based on just the filename from bumpFile. So if bumpFile contains "../../twizzlers.txt" then the system command creates the file tempLoc_twizzlers.txt in the same folder that twizzlers.txt exists in.
Then the perl script opens the already existing tempLoc_twizzlers.txt file (I *think* for read-only purposes seems to be the default when not specified) and then it opens the file loc_analyzer_twizzlers.txt for writing.