Regexp (not in string) in perl - regex

Question

Okie, I have the following files:
total 32
drwxr-xr-x 12 al staff 408B Feb 28 11:36 ./
drwxr-xr-x+ 40 al staff 1.3K Feb 28 10:07 ../
drwxr-xr-x 3 al staff 102B Oct 19 20:38 Install OS X Yosemite.app/
-rw-r--r-- 1 al staff 7B Dec 15 13:35 file1
-rw-r--r-- 1 al staff 4B Dec 15 13:35 file2
-rw-r--r-- 1 al staff 11B Dec 15 13:35 file3.part
-rw-r--r-- 1 al staff 0B Feb 28 11:36 file4.art
-rwxr-xr-x 1 al staff 1.9K Feb 28 11:35 show.pl*
drwxr-xr-x 2 al staff 68B Feb 28 10:07 test1/
drwxr-xr-x 6 al staff 204B Feb 28 10:12 test2/
drwxr-xr-x 3 al staff 102B Feb 28 10:07 test3/
drwxr-xr-x 3 al staff 102B Feb 28 10:12 test4/
Now I need a regexp that will do the following:
3 or more characters (to omit . and ..) of any type NOT ending in the string .part (but ending in anything else is OK).
The following almost works, but it will not match .app and .art (which it should).
print $file =~ m/^.{3,}[^(\.part)]$/i;
And please believe me when I say... I have TRIED (for a loooong time)

Answer 1

You need to use a negative lookahead assertion at the start.
print $file =~ m/^(?!.*\.part$).{3,}/i;
DEMO
Asserts that the string going to be matched won't contain .part string at the last. If yes, then match the string which has three or more characters. $ asserts that we are at the end.