Filesys::DF module provides a way to obtain filesystem disk space information.

df() requires a argument that represents the filesystem you want to
query. The argument can be either a scalar directory/file name or a
open filehandle. There is also an optional block size argument so you
can tailor the size of the values returned. The default block size is
1024. This will cause the function to return the values in 1k blocks.
If you want bytes, set the block size to 1.

df() returns a reference to a hash. The keys available in the hash are as follows:
{blocks} {bfree} {bavail} {used} {per}.