This command is used to extract lattice chain conformations from
a MONSSTER trajectory file. The trajectory file is either read from standard
input or can be specified as the second command line argument.
The first argument is required to select a frame within the trajectory file
by the number of the temperature step and the number of the cycle within that step.
Both numbers have to be separated by a colon.
xtracttra.pl 5:10 1vii.monsster.trajectory
extracts a MONSSTER chain file at cycle 10 of time step 5 from the given trajectory file