$ cat a
2
$ ruby -nle 'puts $_.gsub(/2/,"two")' a
two
$ 

seq 10 | ruby -ne 'sum||=0;sum+=$_.to_i;END{puts sum}'
# => 55

ruby -nle 'puts $_ if $_ =~ /^abc/' file

ruby -e "puts ('a'..'z').to_a" | while read line; do echo ${line}; done