why multiple variables monomials got error, how to run this

LIB "homolog.lib";
int p = printlevel;
printlevel= 1;
ring r = 0,(a*b*c,a*c,b*c,c),dp;
module M = [0,1,0],[0,0,1],[1,0,0];
module A = [0,1,1],[1,0,1],[1,1,0];
module H = Hom(M,A);

below can run, but above got error

LIB "homolog.lib";
int p = printlevel;
printlevel= 1;
ring r = 0,(a,b,c),dp;
module M = [0,1,0],[0,0,1],[1,0,0];
module A = [0,1,1],[1,0,1],[1,1,0];
module H = Hom(M,A);



int p = printlevel;
> printlevel= 1;
> ring r = 0,(a*b*c,a*c,b*c,c),dp;
? `a` is not defined
? error occurred in or before STDIN line 4: `ring r = 0,(a*b*c,a*c,b*c,c),dp;`
? expected ring-expression. type 'help ring;'
> module M = [0,1,0],[0,0,1],[1,0,0];
? no ring active
? `module` is undefined
? error occurred in or before STDIN line 5: `module M = [0,1,0],[0,0,1],[1,0,0];`
> module A = [0,1,1],[1,0,1],[1,1,0];
? no ring active
? `module` is undefined
? error occurred in or before STDIN line 6: `module A = [0,1,1],[1,0,1],[1,1,0];`
> module H = Hom(M,A);
? no ring active
? `module` is undefined
? error occurred in or before STDIN line 7: `module H = Hom(M,A);`
>