Questions about regular expressions

redist

What is the regular expression of email in POSIX, I wrote
eregi ('^ ([_. 0-9a-z]) + @ ([_ 0-9a-z-]) +. ([0-9a-z _-.]) +', "luan78zao@hotmail.com" , $ validated);
But return is false, is there an error? Also shown on the page
Warning: eregi () [function.eregi]: REG_ERANGE in C:\AppServ\www\finalProject\validatePage.php on line 8
What does this mean? Thank you all masters

nfbjyqxshe

The period symbol matches all characters, including spaces, tab characters, and even newlines.
Hyphen ("-") It represents a range.
Therefore, to match these two characters, use "\" to escape
The proper expression can be
eregi ("^ [_\.0-9a-z-] + @ ([0-9a-z] [0-9a-z-] +\.) + [az] {2,3} $", 'luan78zao @ hotmail.com ', $ validated);