In Tcl, commands and their arguments are delimited by white space. However, all XSPEC command are treated as a Tcl command having one `argument', which is then parsed internally by XSPEC. Thus, arguments for XSPEC commands can be delimited by either spaces or commas, as was also the case with previous versions of XSPEC. A command can be terminated by either a newline or a semicolon. Thus multiple commands separated by semicolons can be on the same line.
The # sign is used for comments in Tcl, but may appear only at the
beginning of a command. The \ character is used for continuing a
command onto the next line.