Within any script in AppleScript you can use any shell command, thus you can run any UNIX executable from any script in Smile.
This relies on the do shell script command, a standard command in AppleScript under MacOS X. Executing do shell script [someCommandLine] from an applescript is like executing someCommandLine in a Terminal window (except that do shell script invokes /bin/sh while Terminal uses tcsh by default).
For all details about the do shell script command see Apple's TN2065.
set x to "Reagan
Bush
Clinton
Bush"
do shell script "echo " & x & "|tr '\\r' '\\n'|sort|uniq"
-- Result:
Bush
Clinton
Reagan
The example below would run a code named spl using a file named f_in as input, and would return the result as a string into the variable s.
-- assume f_in is the POSIX path to some data file with extension .ctl
set f_out to change ".ctl$" into ".out" in f_in with regexp
set sh_scpt to "/sw/bin/spl " & f_in & " > & " & f_out
do shell script sh_scpt
set s to read POSIX file f_out
AppleScript and UNIX use different conventions for file paths. For details read the page below.