perl 变量

#! C:/Program Files/Apache Software Foundation/usr/bin/perl.exe

# scriptname hello.pl

$a =33;
print "Content-type:text/html\n\n";
print "hello..\n";
print $a;
++++++++++++++++++++++++++++++
$a=29E-23;-----科学计数法，中间是连词符，加号左边的减号，不是下滑线。