egrep '\<(Königst|T)ochter\>' frosch.txt

grep :/bin/bash$ /etc/passwd

k='[^aeiou]*'
grep -i ^${k}a${k}e${k}i${k}o${k}u${k}$ /usr/share/dict/words

egrep '(\<[[:alpha:]]{4,}\>).*\<\1\>' frosch.txt