regex - Can anyone explain this regular expression to me in detail? -

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i have regex here , need know if 100% omit bad email addresses not understand them need call on community experts.

the string follows:

^[_a-za-z0-9-]+(.[_a-za-z0-9-]+)*@[a-za-z0-9-]+(.[a-za-z0-9-]+)*(.[a-za-z]{2,3})$

thank in advance!

^[_a-za-z0-9-]+(.[_a-za-z0-9-]+)*@[a-za-z0-9-]+(.[a-za-z0-9-]+)*(.[a-za-z]{2,3})$

piece piece

    ^  start of string      [_a-za-z0-9-]+ 1 or more characters of "_" (no quotes), letter (a-z, a-z), number (0-9), or "-" (no quotes)     (.[_a-za-z0-9-]+)* 0 or more substrings of type .something, or .123, or .a123. substring must formed . , letter (same group of letters before). "." not valid. ".a" or ".1" or ".-" is.

(up until accept example my.name12 or my.name12.surname34)

    @ "@" (like max@something)      [a-za-z0-9-]+ 1 or more characters same pattern before     (.[a-za-z0-9-]+)* 0 or more substrings of type ".something"... before     (.[a-za-z]{2,3}) "." (dot) , 2 or 3 letters (a-z or a-z)      $ end of string

so have email address, can't have something.@somethingelse.ss (no "dangling" dot before @) or .something@somethingelse.ss (no beginning dot). domain must start letter , can't have dot before first level domain (.com/.uk/??), no something@x..com. first-level domain must have 2 or 3 letters (no numbers)

there error, . (dot) must escaped, should \. . depending on language, \ must escaped in string (so \\.)


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