foreach my $line (@vcvars) {
	if ($line =~ /^set INCLUDE=(.*)/) { ## use the ^ and $ anchors whenever possible
		my @paths = split(/;/, $1); # $1 is the part in brackets in the regex above
		print VCVARS32 "set INCLUDE=";
		print VCVARS32 join(";",  # concatenate list of strings using semicolons
			grep( !/^\%SRVBUILD\%/, @paths) # return list of the strings that do not start with %SRVBUILD%
		);
		print VCVARS32 "\n";
		next;
	}
	# no else{} necessary; next() will prevent you falling through to here

	# in you "set SRVBUILD" case:
	# $line =~ s/^\=(\W*)/\=/;
	# this will not work since you're using an ^ anchor;
	# the "=" is not at the beginning of the string, is it?
	# also, \W matches any NONword-character; anything NOT a letter, digit or underscore
	# but if I understood correctly you want to change everything after the "="

	# you can simply use a s///ubstitution here
	# since if the left side does not match, nothing gets replaced;
	# no need for an if(){}
	s/^(set SRVBUILD)=.*/$1=INI_CODE_HERE/;

	# and then we can just let the boilerplate print handle the modified $line
	print VCVARS32 $line; 
}