egrep finds all the cases because it has greedy alternation(the subject of this Seekers...). -o simply has egrep print out the matches it does find. A complete non-perl solution could be something like

echo 1b22cc333a | egrep -o 'a|b|c' | sort -u | wc -l
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This will simply return 3. If I want 3 chars in any order and this command returns 3 than I had a successful match of all 3 in any order!