This page lets you set up two fragments of HTML which will get pre-loaded into the text editor box any time you're in a position to post a new node (for example, at the bottom of the Seekers of Perl Wisdom page).
You can use the upper part for whatever you want to pre-load in your posts. It is typically used as a template for your posts.
The lower part is treated as a .sig block by PerlMonks. It gets automatically wrapped with special HTML to make it "look like" a signature when people view your nodes.
For more details, see Signatures and Node Templates.
Both parts are optional and may be left blank.
Also read Perl Monks Approved HTML tags and Writeup Formatting Tips. Have fun noding!