Regular expression 

Effect 

. (period) 

Matches any single character. Example: "sampl." would match "sample" or "samplZ" 

^ (caret) 

Matches the start of a line 

$ 

Matches the end of a line 

\ 

Treat next character literally. Example: in "\$100", the indicates that the pattern is "$100", not end-of-line ($) followed by "100" 

[abc] 

Brackets indicate a set of characters, one of which must be present. For example, "sampl[ae]" would match "sample" or "sampla", but not "samplx" 

[a-z] 

Inside brackets, a dash indicates a range of characters. For example, "[a-z]" matches any single lower-case letter. 

[^a-z] 

Indicates any character except the ones in the bracketed range. 

.* (period, asterisk) 

An asterisk means "0 or more" of something, so .* would match any string of characters, or nothing 

.+ (period, plus) 

A plus means "1 or more" of something, so .+ would match any string of at least one character 

[a-z]+ 

Any sequence of one or more lower-case letters.