This will do it, and do it efficiently:

perl -ne 'while(<>) { next if $. < 60; last if $. > 70; print; }' 
wordlist
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The logic’s clear enough and it fits on one line (although I word-wrapped it for clarity):   loop if we’re not at the right starting position, break out of the loop if we’re past it, otherwise print a line.   Virtually no memory is consumed and the loop does not read the whole file.