sloth is a small utility that reads stdin and echoes it back out very, very slowly.
By default, it will sleep for 10ms between input bytes, but you can specify a duration with an argument:
cat list.txt | sloth 25 # sleep for 25 milliseconds per byte
cat list.txt | sloth 3s # sleep for 3 seconds per byte
Supported suffixes:
ms(milliseconds)s(seconds)m(minutes)h(hours)