Regular Expression Perl

Shortcut              Expansion                                       Description
[[:alpha:]]           [a-zA-Z]                                        An alphabetic character.
[[:alnum:]]           [0-9A-Za-z]                                     An alphabetic or numeric character.
[[:digit:]]           \d                                              A digit, 0-9.
[[:lower:]]           [a-z]                                           A lower case letter.
[[:upper:]]           [A-Z]                                           An upper case letter.
[[:punct:]]           [!"#$%&'()*+,-./:;<=>?@\[\\\]^_`{|}~]           A punctuation character â€“ note the escaped characters [, \, and ].
/bea?t/ Matches either 'beat' or 'bet'
/bea+t/ Matches 'beat', 'beaat', 'beaaat'…
/bea*t/ Matches 'bet', 'beat', 'beaat'…