# show the current unix timestamp
perl -le 'print time'

# prints the rollover moment for your timezone (from ChemBoy)
perl -le 'print scalar localtime 1e9'

# count up to rollover (from abigail)
perl -le 'sleep 1 while print time'

# count down to rollover
perl -le 'sleep 1 while print 1e9-time'

# count in both direction on a vt100 term (modified from one of MrNobo1024's)
clear; perl -le 'sleep 1 while print "\e[1A", 1e9 - time, " ==> ", time'