STATS MAKE ME CRY

Dear Statistician:

I am trying to program ivregress 2sls function in Mata and i
have following mata code, but i get error that number of names and number of
cols do not match:

Is it possible to program ivregress 2sls with this syntax, meaning passing
all dep, indep and instrument variables together, or do i need to pass
instrument variable separately.

capture mata mata drop m_ivols()
version 10
mata
void m_ivols(string scalar varlist, string scalar touse)
{
real matrix M, X, V,Pz, PzX, PzY
real colvector y, b, Z
real scalar n, k, s2

M = X = y = Z = .
st_view(M, ., tokens(varlist), touse) // Whole data set
st_subview(y,M,.,1) // 1st column dep variable
st_subview(Z,M,.,2) // 2nd column instrument variable (only 1
instrument)
st_subview(X,M,.,(3\.)) // 3rd to last column all indep variables

n=rows(X)
k=cols(X)+1
Pz = Z*invsym(Z'*Z)*Z'
PzX = Pz*X
PzY = Pz*y
XX=cross(X,1,PzX,1)
Xy=cross(X,1,Pzy,0)
b=cholsolve(XX,Xy)
e=y-(X,J(n,1,1))*b
s2=(e'e)/(n-k)
V=s2*cholinv(XX)

st_eclear()
st_matrix("r(b)",b)
st_matrix("r(V)",V)
st_numscalar("r(N)",n)
}
end

***************************************************************************

capture program drop m_ivols()
program define ivols, eclass
version 10.0
syntax varlist(numeric) [if] [in]
gettoken depvar indepvar: varlist
marksample touse

mata: m_ols("`varlist'","`touse'")

tempname b V
matrix `b'=r(b)'
matrix `V'=r(V)
local N=r(N)

matname `b' `indepvar' _cons, c(.)
matname `V' `indepvar' _cons
ereturn post `b' `V', depname (`depvar') obs(`N') esample(`touse')
ereturn local cmd="ols"
ereturn display
end

I will really appreciate if some one can help me with this problem.

Thanks Harshil