A regular expression is a concise way of expressing any pattern of characters.
You construct a regular expression by combining ordinary characters with one or more metacharacters: characters that have special meaning.
The following characters can be used to create regular expressions for searching.
To look up only Onatrio callsigns with two character suffixes, you would use 'v.3..$'
Suppose heard a members VE3 callsign but couldn't make the suffix but were sure it started with 'T', 'V' or 'C', use the search string 've3[tvc]..'