On startup, slipknot presents you with a text field for entering the absoulte file path to your lasso file(s). You can convert one file at a time, or an entire directory recursively. Directories should be entered with a trailing slash.
If the Display On Screen radio button is checked, slipknot will not write the file to the filesystem, but will only display the old lasso code and the new php code for you to preview. If the Write to File or Convert Entire Project (recursive) options are checked, the translated file(s) will be written alongside the .lasso files.
Most lasso tags have some sort of analog in php. Those that don't use functions in the lib.slipknot.php file (like lassoMicrotime() or lassoInclude()). The script uses a looping perl regular expression to find code blocks nested in parentheses or square brackets. If it recognizes a match as a lasso tag, it converts it to a php function.