Here are some examples of using tmultin:
stilts tmultin nin=3 in1=t1.xml ifmt1=votable
                     in2=t2.fit ifmt2=fits
                     in3=t3.txt ifmt3=ascii
                     out=tables.fits
stilts tmultin nin=3 in1=data.fits icmd1='every 10;   head 100'
                     in2=data.fits icmd2='every 100;  head 100'
                     in3=data.fits icmd3='every 1000; head 100'
                     out=samples.xml ofmt=votable