Macbook Pro file mods
The @ sign means that the files have extended attributes. What you noticed was the extended attribute com.apple.FinderInfo, which can be modified to have Finder hide the file.

Using ls -@, you can see the extended attributes of the file.

This is what shows up when I run ls -dl@ Library when my Library folder is hidden:

drwx------@ 54 me  staff  1836 Aug 31 11:16 Library
     com.apple.FinderInfo   32


and when it is showing (a setting in Show View Options in Finder on your home directory):

drwx------+ 54 me  staff  1836 Aug 31 11:16 Library


The com.apple.FinderInfo   32  means that the file is hidden. (32 is just the bit  they chose to represent it, 1&lt;&lt;5. This is called a bitmask.)

You can hide and show files with chflags hidden and chflags nohidden, enabling and disabling that bit of com.apple.FinderInfo.