Based on CB chat, my current understanding follows:

• You have a Perl script (running as CGI).
• Said script cannot use Image::Magick to access a file ("~/Pictures/wallpapers/:D.jpg") via a symlink ("/var/www/guest/wallpapers/:D.jpg").
• The entire Apache business is a red herring because it finds and executes your script.

Two important points about CGI scripts:

• The current dir is often set to "/".
• The user running the script may not be "you".

Checklist to answer:

• Check if the symlink is named what you expect it to be named.
• Check if the image is named what you expect it to be named.
• Check if the symlink points to the correct file.
• Check if the variable holds the file name you are expecting it to hold. Note that the tilde doesn't mean home dir in a file name unless it's subject to shell expansion.
• Check if the user as which your script runs has sufficient permissions to access the directory containing the symlink. That means it needs to be able to access all the directories in the path that leads to the symlink.
• Check if the user as which your script runs has sufficient permissions to read the directory containing the links.
• Check if the user as which your script runs has sufficient permissions to access the directory containing the image. That means it needs to be able to access all the directories in the path that leads to the image.
• Check if the user as which your script runs has sufficient permissions to read the image?
• Check the error you are getting by opening the symlink using open instead of Image::Magick.
• Check the error you are getting by opening the image using open instead of Image::Magick.

Update: Added a couple more.