钻石操作符

#! /usr/bin/perl
use strict;
use warnings;

=pod
print " -----------------------------while(defined($equal_sign = <>))------------------------------- ";
my $forwar_slash;
while(defined($forwar_slash = <>)){
    chomp($forwar_slash);
    print "$forwar_slash "
}
print " -----------------------------while(defined($equal_sign = <>))------------------------------- ";
=cut

=head1
print " ---------------------------while(<>)--------------------------------- ";
while(<>){
    chomp;
    print "$_ ";
}
print " ---------------------------while(<>)--------------------------------- ";
=cut

=head1
print " ----------------------------@ARGV-------------------------------- ";
foreach(@ARGV){
    print $_;
}
print "foreach_end. ";
my $metacharacter = shift(@ARGV);
$metacharacter = shift(@ARGV);
print $metacharacter;
print " ----------------------------@ARGV-------------------------------- ";
=cut

=head1
print " ---------------------------------_mannually_mod_@ARGV--------------------------- ";
@ARGV = qw{pl.pl pl.pl};
while(<>){
    chomp;
    print "$_ ";
}
print " ---------------------------------_mannually_mod_@ARGV--------------------------- ";
=cut1

print " ---------------------------------array_element_with_carriage_return_--------------------------- ";
my @minus_sign = qw{ notation angle_brackets at_sign };
print @minus_sign;
print " ";
print "@minus_sign";
print " ---------------------------------array_element_with_carriage_return_--------------------------- ";

print " ---------------------------------print_as_func_call_with_parentheses--------------------------- ";
print (2+3)*4;
print " ---------------------------------print_as_func_call_with_parentheses--------------------------- ";

print " ---------------------------------printf_--------------------------- ";
printf "username:%s.   password:%s.", $minus_sign[0], $minus_sign[1];
print " ---------------------------------printf_--------------------------- ";

print " ---------------------------------printf_%g_aoto_select_num_format_--------------------------- ";
printf "NO 1: %g, NO 2: %g, NO 3: %g.", 5/2, 51/17, 51 ** 17 ;
print " ---------------------------------printf_%g_aoto_select_num_format_--------------------------- ";

print " ---------------------------------_percent_sign--------------------------- ";
printf "Monthly interest rate: %.2f%% ", 5.25/12;
print " ---------------------------------_percent_sign--------------------------- ";

print " ---------------------------------store_format_string_2_scala_--------------------------- ";
my @dollar_underscore = qw { wilma dino pebbles };
my $semicolons = "The items are: ".("%10s " x @dollar_underscore);
printf $semicolons, @dollar_underscore;
print " ---------------------------------store_format_string_2_scala_--------------------------- ";

print " ---------------------------------cooleset_--------------------------- ";
printf"The items are: ".("%10s " x @dollar_underscore), @dollar_underscore;
print " ---------------------------------cooleset_--------------------------- ";

print " ---------------------------------backslash_percent_sigh_--------------------------- ";
print "\%";
print " ---------------------------------backslash_percent_sigh_--------------------------- ";

print " ---------------------------------_--------------------------- ";