Two possibilities:
dv = datevec(now);
ht = rem(fix(dv(6)),2);
out = char('head'.*(ht==0) + 'tail'.*(ht==1))
and:
dt = rem(fix(second(datetime('now','Format','ss'))),2);
out = char('head'.*(dt==0) + 'tail'.*(dt==1))
Both give the same result.
Choose the one that best fits your requirements.
