Now you are a programming expert. I will ask you grammar questions and you will provide a comparison table of the syntax for Bash, Tcl, and Perl in markdown format based on my questions. Please reply in Chinese.
1、 if(){} 2、 if(){}else {} 3、 if(){}elsif(){}else{} unless(){} (和if相反,if是条件成立执行,unless是条件不成立执行语句) 和if相同有1、2、3 switch语句 语法格式: use Switch; switch(argument){ case 1 { print "数字 1" } ...
#!/usr/bin/perl $bar = "This is foo and again foo"; if ($bar =~ m[foo]) { print "First time is matching\n"; } else { print "First time is not matching\n"; } $bar = "foo"; if ($bar =~ m{foo}) { print "Second time is matching\n"; } else { print "Second time...
<bulk88> I've thought for years, PERL_SYS_INIT3 macro needs a secret setjmp() in it. Since a PERL_SYS_INIT/PERL_SYS_TERM pair, look perfect to slide in, secret MS C89 try{}/catch{} syntax if Perl's setjmp() exceptions are ever turned into formal MS-C89 SEH exceptions. <bulk...
# elsif 就是 else if # 如果指令(statement)只有一项,我们可以使用倒装句法,看起来比较简洁。 statement if (Expression); # unless 就是if not statement unless (Expression);例: print "HELLO!\n" if ($name eq "friend"); $x-=10 if ($x == 100); ...
elseif should be elsif (S syntax) There is no keyword "elseif" in Perl because Larry thinks it's ugly. Your code will be interpreted as an attempt to call a method named "elseif" for the class returned by the following block. This is unlikely to be what you want. Empty %s (F) ...
return 0 if scalar @_ == 0; return 2 * $_[0]; } use warnings; use strict 'refs'; print double(-3); syntax OK 很清楚地发现,perl把 double -3 理解成了 double(-3)。为了避免这种问题,在函数调用的时候,我们必须明确地写成 double() - 3 ,而如果你就是想表达 double(-3) 的话,也要明...
IF, ELSIF, ELSE, and UNLESS The primarydirective forconditional executionis theIFstatement. The basic syntax is: [% IF test %] action [% END %] whereactionis executed only iftestis true (the Template Toolkit’s definition of “truth” is explained later in this section).IFstatements allow...
NO! SYNTAX ERROR 因为Perl将把/解释为正则表达式的结束标记。这里有三种方法去匹配类似于上述特殊字符的方法。第一种方法是利用反料杠来“转义”想匹配的任意特殊字符一包括反斜杠。因而刚才给出的例子可变为: $path =~ m///usr//local//bin/; 该程序尽力匹配 $path中的/usr/local/bin。第二种方法是使用...
#if结构是变化最小的,你仍然可以用elsif和else,unless也还在,但是在unless前面不允许else 2: #分支结构 3: if $sheep == 0 {say "how boring";} 4: elsif $sheep ==1 {say "one lonely sheep";} 5: else {say "a herd,How lovely!";} ...