procedure main(arglist)
write("Usage: substring  <string> <first position> <second position> <single character> <substring>")
s := \arglist[1] | "aardvarks"
n := \arglist[2] | 5
m := \arglist[3] | 4
c := \arglist[4] | "d"
ss := \arglist[5] | "ard"

write( s[n+:m] )
write( s[n:0] )
write( s[1:-1] )
write( s[find(c,s)+:m] )
write( s[find(ss,s)+:m] )
end