is the best... syntax highlighting, line numbering, the ability to add/create your own add-in tools, macros, workspaces... tons of stuff.
For instance, my tools menu in Textpad has "Perl - Check syntax", "Perl - Run in Console", and "Perl - Capture output", all of which act on the currently open file. I've also written my own "plug-ins" for Textpad in Perl, such as Dictionary/Thesaurus lookups, and the ability to send someone the open document simply by entering an e-mail address.
Plus, it's very fast, and only $27.
Alan "Hot Pastrami" Bellows