203 lines
11 KiB
Markdown
203 lines
11 KiB
Markdown
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title: '『新版Perl言語プログラミングレッスン入門編』第6章: 繰り返し のつづき'
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author: kazu634
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date: 2008-02-07
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url: /2008/02/07/_842/
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wordtwit_post_info:
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- 'O:8:"stdClass":13:{s:6:"manual";b:0;s:11:"tweet_times";i:1;s:5:"delay";i:0;s:7:"enabled";i:1;s:10:"separation";s:2:"60";s:7:"version";s:3:"3.7";s:14:"tweet_template";b:0;s:6:"status";i:2;s:6:"result";a:0:{}s:13:"tweet_counter";i:2;s:13:"tweet_log_ids";a:1:{i:0;i:3701;}s:9:"hash_tags";a:0:{}s:8:"accounts";a:1:{i:0;s:7:"kazu634";}}'
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categories:
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- Perl
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---
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<div class="section">
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<p>
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つづきー
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</p>
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<p>
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<a name="seemore"></a>
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</p>
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<h4>
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while
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</h4>
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<p>
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繰り返しの中でlastを使うと、繰り返しを終了するよ。次のプログラムは「END」という行があったらそこで繰り返しを終了している。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">my</span> <span class="synIdentifier">@array</span> = (<span class="synConstant"></span>, <span class="synConstant">1</span>, <span class="synConstant">2</span>, <span class="synConstant">3</span>, <span class="synConstant">4</span>, <span class="synConstant">5</span>, <span class="synConstant">6</span>, <span class="synConstant">7</span>, <span class="synConstant">8</span>, <span class="synConstant">9</span>);
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<span class="synStatement">my</span> <span class="synIdentifier">$flag</span> = <span class="synConstant"></span>;
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swhile (<span class="synIdentifier">$flag</span> < <span class="synConstant">10</span>) {
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<span class="synIdentifier">$flag</span> = <span class="synIdentifier">$flag</span> + <span class="synConstant">1</span>;
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<span class="synStatement">if</span> (<span class="synIdentifier">$array</span>[<span class="synIdentifier">$flag</span>] == <span class="synConstant">5</span>){
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<span class="synStatement">last</span>;
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}
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<span class="synStatement">print</span> <span class="synConstant">"</span><span class="synIdentifier">$array</span><span class="synConstant">[</span><span class="synIdentifier">$flag</span><span class="synConstant">]</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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}
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</pre>
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<p>
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こいつはこんな風に書き換えることも可能。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">my</span> <span class="synIdentifier">@array</span> = (<span class="synConstant"></span>, <span class="synConstant">1</span>, <span class="synConstant">2</span>, <span class="synConstant">3</span>, <span class="synConstant">4</span>, <span class="synConstant">5</span>, <span class="synConstant">6</span>, <span class="synConstant">7</span>, <span class="synConstant">8</span>, <span class="synConstant">9</span>);
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<span class="synStatement">my</span> <span class="synIdentifier">$flag</span> = <span class="synConstant"></span>;
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<span class="synStatement">while</span> (<span class="synIdentifier">$flag</span> < <span class="synConstant">10</span>) {
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<span class="synIdentifier">$flag</span> = <span class="synIdentifier">$flag</span> + <span class="synConstant">1</span>;
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<span class="synStatement">last</span> <span class="synStatement">if</span> (<span class="synIdentifier">$array</span>[<span class="synIdentifier">$flag</span>] == <span class="synConstant">5</span>);
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<span class="synStatement">print</span> <span class="synConstant">"</span><span class="synIdentifier">$array</span><span class="synConstant">[</span><span class="synIdentifier">$flag</span><span class="synConstant">]</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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}
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</pre>
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<p>
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こっちの方がスマートだ。
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</p>
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<p>
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繰り返しの中でnextを使うと、繰り返しを「次」に進めます。たとえば次のようなプログラムだと、配列の5番目をスキップして表示することになるよ。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">my</span> <span class="synIdentifier">@array</span> = (<span class="synConstant"></span>, <span class="synConstant">1</span>, <span class="synConstant">2</span>, <span class="synConstant">3</span>, <span class="synConstant">4</span>, <span class="synConstant">5</span>, <span class="synConstant">6</span>, <span class="synConstant">7</span>, <span class="synConstant">8</span>, <span class="synConstant">9</span>);
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<span class="synStatement">my</span> <span class="synIdentifier">$flag</span> = <span class="synConstant">-1</span>;
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<span class="synStatement">while</span> (<span class="synIdentifier">$flag</span> < <span class="synConstant">10</span>) {
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<span class="synIdentifier">$flag</span> = <span class="synIdentifier">$flag</span> + <span class="synConstant">1</span>;
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<span class="synStatement">next</span> <span class="synStatement">if</span> (<span class="synIdentifier">$array</span>[<span class="synIdentifier">$flag</span>] == <span class="synConstant">5</span>);
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<span class="synStatement">print</span> <span class="synConstant">"</span><span class="synIdentifier">$array</span><span class="synConstant">[</span><span class="synIdentifier">$flag</span><span class="synConstant">]</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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}
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</pre>
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<p>
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他にもredoとかあるよ。
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</p>
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<h4>
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for
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</h4>
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<p>
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for文の構文は
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">for</span> (初期化; 条件式; 次の一歩) {
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繰り返して実行する部分
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}
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</pre>
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<p>
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となるよ。例はこんな感じ。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">for</span> (<span class="synStatement">my</span> <span class="synIdentifier">$i</span> = <span class="synConstant"></span>; <span class="synIdentifier">$i</span> < <span class="synConstant">10</span>; <span class="synIdentifier">$i</span>++) {
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<span class="synStatement">print</span> <span class="synConstant">"</span><span class="synIdentifier">$i</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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}
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</pre>
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<p>
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こいつはCライクな書き方だけど、perlではこれは次のように書くこともできる。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">for</span> (<span class="synConstant"></span> .. <span class="synConstant">9</span>) {
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<span class="synStatement">print</span> <span class="synConstant">"</span><span class="synIdentifier">$_</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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}
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</pre>
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<h4>
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do .. untilによる繰り返し
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</h4>
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<p>
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do … until構文を使うと、条件判定をはじめに行うのではなく最後に行うことができます。次の文は、標準入力から入力された文字列を表示し、endが入力されると終了します。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">my</span> <span class="synIdentifier">$line</span>;
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<span class="synStatement">do</span> {
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<span class="synIdentifier">$line</span> = <span class="synIdentifier"><STDIN></span>;
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<span class="synStatement">print</span> <span class="synIdentifier">$line</span>;
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} <span class="synStatement">until</span> (<span class="synIdentifier">$line</span> <span class="synStatement">eq</span> <span class="synConstant">"end</span><span class="synSpecial">\n</span><span class="synConstant">"</span>);
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</pre>
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<p>
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do … while構文で書くこともできるけど、そのときは真偽が逆になることに注意してね。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">my</span> <span class="synIdentifier">$line</span>;
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<span class="synStatement">do</span> {
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<span class="synIdentifier">$line</span> = <span class="synIdentifier"><STDIN></span>;
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<span class="synStatement">print</span> <span class="synIdentifier">$line</span>;
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} <span class="synStatement">while</span> (<span class="synIdentifier">$line</span> <span class="synStatement">ne</span> <span class="synConstant">"end</span><span class="synSpecial">\n</span><span class="synConstant">"</span>);
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</pre>
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<h4>
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文字列の繰り返し
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</h4>
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<p>
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演算子xを用いると、文字列の繰り返しを作ることができます。例えば次の文は’-‘を40個表示します。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">print</span> <span class="synConstant">'-'</span> x <span class="synConstant">40</span>, <span class="synConstant">"</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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</pre>
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<p>
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次のようにすると、文字列$strに合わせて横線の長さが上下するよ。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">my</span> <span class="synIdentifier">$str</span> = <span class="synConstant">'Lord Jim: the Failure of Education'</span>;
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<span class="synStatement">print</span> <span class="synConstant">'-'</span> x <span class="synStatement">length</span>(<span class="synIdentifier">$str</span>), <span class="synConstant">"</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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<span class="synStatement">print</span> <span class="synIdentifier">$str</span>, <span class="synConstant">"</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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<span class="synStatement">print</span> <span class="synConstant">'-'</span> x <span class="synStatement">length</span>(<span class="synIdentifier">$str</span>), <span class="synConstant">"</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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</pre>
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<h4>
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grepによる繰り返し
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</h4>
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<p>
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関数grepは配列の中をすべてgrepする。
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</p>
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<pre class="syntax-highlight">
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<span class="synStatement">use strict</span>;
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<span class="synStatement">use warnings</span>;
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<span class="synStatement">my</span> <span class="synIdentifier">@word</span> = (<span class="synConstant">'Sun'</span>, <span class="synConstant">'Mon'</span>, <span class="synConstant">'Tue'</span>, <span class="synConstant">'Wed'</span>, <span class="synConstant">'Thu'</span>, <span class="synConstant">'Fri'</span>, <span class="synConstant">'Sat'</span>);
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<span class="synStatement">my</span> <span class="synIdentifier">@found</span> = <span class="synStatement">grep</span>(<span class="synStatement">/</span><span class="synConstant">^S</span><span class="synStatement">/</span>, <span class="synIdentifier">@word</span>);
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<span class="synStatement">print</span> <span class="synConstant">"</span><span class="synIdentifier">@found</span><span class="synSpecial">\n</span><span class="synConstant">"</span>;
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</pre>
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<h4>
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mapによる繰り返し
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</h4>
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<p>
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後で書く。
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</p>
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</div>
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