$ cp z.pl /ram; perl /ram/z.pl
Check file before unlink
/ram/z.pl
Filesystem           1K-blocks      Used Available Use% Mounted on
none                       100         4        96   4% /ram
Unlinking the file /ram/z.pl
Check file after unlink
ls: /ram/z.pl: No such file or directory
Filesystem           1K-blocks      Used Available Use% Mounted on
none                       100         4        96   4% /ram
File should be now be gone from disk (but still in memory)
Try ^Z and check it with 'ls /ram/z.pl' ... (come back with 'fg')
I'm still here, but the original file is long gone.
$ df -k /ram
Filesystem           1K-blocks      Used Available Use% Mounted on
none                       100         0       100   0% /ram