cheat sheets.

$ command line ruby cheat sheets
A regexp's form is written /pattern/modifiers where "pattern" is the regular expression itself, and "modifiers" are a series of characters indicating various options.

(see an alternate/more complete cheat-sheet with 'cheat regex')

/i makes match case insensitive.
/m makes the dot match newlines.
/o causes any #{...} substitutions in a particular regex literal to be performed just once, the first time it is evaluated. Otherwise, the substitutions will be performed every time the literal generates a Regexp object.

[] 	range specification (e.g., [a-z] means a letter in the range a to z)
\w 	letter or digit; same as [0-9A-Za-z]
\W 	neither letter or digit
\s 	space character; same as [ \t\n\r\f]
\S 	non-space character
\d 	digit character; same as [0-9]
\D 	non-digit character
\b 	backspace (0x08) (only if in a range specification)
\b 	word boundary (if not in a range specification)
\B 	non-word boundary
* 	zero or more repetitions of the preceding
+ 	one or more repetitions of the preceding
{m,n} 	at least m and at most n repetitions of the preceding
? 	at most one repetition of the preceding; same as {0,1}
| 	either preceding or next expression may match
() 	grouping

print "success" if subject =~ /regex/

result = subject.gsub(/before/, "after")

myarray = mystring.scan(/delimiter/)