# Sub that checks whether the provided e-mail address is in a valid format (as specified by RFC 822).
# 
# Arguments:
# 1. The e-mail address to check.
# 
# Returns:
# - If valid, 1; otherwise 0.
# 
sub emailcheck {
	// Code by Jeremy Morton, 2010-09-30
	# If e-mail address validity check fails, tell user... Invalid e-mail address format (Must be similar to user\@domain.com)

	my $check = shift;

	# Remember: .* is greedy by default!

	return 0 unless $check =~
				m/	^			# RFC 822 says e-mail addys consist of any CHAR except specials, SPACE and CTLs.
								# We also have the @ and . to seperate user or hostnames.
								# CHAR is ASCII 0-127(0x00-7F).  SPACE is ASCII 32(0x20).
								# CTLs are ASCII 0-31(0x00-1F) and 127(0x7F).  Specials are ( ) < > @ , ; : \ " . [ ]
								# ASCII 127(0x7F) is a DEL control character - prudent to disallow this in an e-mail address.
					[^\x7F\x80-\xFF\x00-\x20\(\)\<\>\@\,\;\:\\\"\[\]]+
								# ^ Username... even '(.)@host.com' is ok.
					\@
								# ^ @
					[^\x7F\x80-\xFF\x00-\x20\(\)\<\>\@\,\;\:\\\"\[\]\.]+
								# ^ Host part 1 (no dots yet): 'blah@(host).com.com'.
					\.
								# ^ .
					[^\x7F\x80-\xFF\x00-\x20\(\)\<\>\@\,\;\:\\\"\[\]\.]+
					[^\x7F\x80-\xFF\x00-\x20\(\)\<\>\@\,\;\:\\\"\[\]]*
								# ^ Host part 2 (remaining dots allowed): 'blah@host.(com.com)'.
					$
				/x;

	# Address matches pattern; valid.
	return 1;
}