procedure main(A)
   every write(s := !A,": ",(repString(s) | "Not a rep string!")\1)
end

procedure repString(s)
    rs := s[1+:*s/2]
    while (*rs > 0) & (s ~== lrepl(rs,*s,rs)) do rs := rs[1:-1]
    return (*rs > 0, rs)
end

procedure lrepl(s1,n,s2)   # The standard left() procedure won't work.
    while *s1 < n do s1 ||:= s2
    return s1[1+:n]
end