You can combine several metacharacters in one regular expression. One of the most common combinations is the period and asterisk (.*) which matches a string of any length including the null string.
Regular Expression
Matches
Reason
.*\.cgi$
any string ending in .cgi
The period and asterisk (.*) combination matches any string. The backslash (\) tells NetTracker to look for a period, not use the period as a metacharacter.
.*.cgi$
acgi
thomcgi
file.cgi
The second period is not preceded by a backslash (\), so it is being used as a metacharacter to match any one character no matter what the character is.