Differences

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--- notes:perl_cheat_sheet [2013/09/22 14:20]
smthng [Lists and Arrays]
+++ notes:perl_cheat_sheet [2013/09/22 19:28] (current)
smthng [Hashes]
@@ Line 70: / Line 70: @@
   * To initialize a hash :<code perl>%some_hash = ('a', 1, 'b', 2, 'c', 3);
 %some_hash = ( 'a' => 1, 'b'=>2, 'c'=>3,);</code>
-  * When using an arrow (a fat-comma), simple keys don't have to be quoted (barewords) .
+  * When using a big arrow (a fat-comma) or when accessing a value, simple keys don't have to be quoted (barewords) e.g. <code perl>%some_hash = ( a => 1}; $some_hash{a};</code>
+  * ''%revhash = reverse %hash'' to reverse a hash (for non-unique values, last one wins).
+  * ''keys %hash;'' and ''values %hash;'' return a list of keys or value in same order (or # of keys/values in scalar context).
+  *  '' %hash'' is true only if hash has at least one key-value pair.
+  * To iterate over hash : <code perl>while ( ($key, $value) = each %hash ) {
+  print "$key => $value\n"; }</code> or in order of keys <code perl>foreach $key (sort keys %hash) {
+  print "$key => $hash{$key}\n"; } </code>
+  * %ENV hash holds environment variables.
 ===== Control Structures =====