#start of login.cgi

open(FILE, "file.log");
flock(FILE, LOCK_EX);
print FILE "$a:$b:$c\n";
close FILE;

#call function
function;

return 0;
#end of login.cgi
-------------------
;#start of login.pl

sub function
{
open(FILE, "file.log");
flock(FILE, LOCK_EX);

$a = <FILE>;
print "line: $a\n";
close FILE;
#end of login.pl
1;