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--- notes:perl_cheat_sheet [2026/09/15 05:45]
163.7.15.111 old revision restored (2013/08/31 23:24)
+++ notes:perl_cheat_sheet [2026/09/16 14:25] (current)
216.73.216.94 old revision restored (2026/09/15 14:12)
@@ Line 14: / Line 14: @@
   * Parenthesis are optional unless part of syntax.
+===== Numbers =====
+  * All numbers are stored in the same format e.g.-6.5e24, 037 (octal), 0x2a13b (hex), 0b11010 (binary)
+  * Underscores for readability are ignored e.g. 0x1377_0B77
+  * Arithmetic operators are * / + - % (modulus) %%**%% (exponentiation)
+  * Comparison operators are < <= == >= > !=
+===== Strings =====
+  * To use unicode in source code - "use utf8;"
+  * Single-quoted literals '⅚∞☃☠' can contain any character except single-quote (use \') and backslash (use \\).
+  * Double-quoted strings can contain control-characters starting with a backslash and are variable interpolated e/g/ "${var}s $var\n".
+  * . is for concatenation, x for string repetition.
+  * To insert a character by code - chr(0x05d0). To convert a character to its code - ord('א')
+  *  String comparison operators are lt, le, eq, ge, gt, and ne
 ===== Scalar Variables =====
@@ Line 41: / Line 56: @@
   * ''unshift'' adds element(s) to **start** of array. ''shift'' removes a single element and returns it.
   * ''splice'' removes elements from middle of array, returns them and optionally replaces them <code perl>splice @arr, start, len, @newelems</code>
-===== Numbers =====
+  * ''sort'' and ''reverse'' functions return the modified list (can be saved to original array variable).
+  * Expressions parsed in either a scalar context or a list context. Scalars are promoted to single-element lists in list context.
-  * All numbers are stored in the same format e.g.-6.5e24, 037 (octal), 0x2a13b (hex), 0b11010 (binary)
+  * List functions may return different scalars - array variables return number of elements. The ''scalar'' function forces a scalar context e.g. for print function.
-  * Underscores for readability are ignored e.g. 0x1377_0B77
-  * Arithmetic operators are * / + - % (modulus) ** (exponentiation)
-  * Comparison operators are < <= == >= > !=
-===== Strings =====
-  * To use unicode in source code - "use utf8;"
-  * Single-quoted literals '⅚∞☃☠' can contain any character except single-quote (use \') and backslash (use \\).
-  * Double-quoted strings can contain control-characters starting with a backslash and are variable interpolated e/g/ "${var}s $var\n".
-  * . is for concatenation, x for string repetition.
-  * To insert a character by code - chr(0x05d0). To convert a character to its code - ord('א')
-  *  String comparison operators are lt, le, eq, ge, gt, and ne
 ===== Control Structures =====
@@ Line 70: / Line 74: @@
 }</code>
   * foreach loop <code perl>foreach $rock (@rocks) {
   # modifications to $rock modify the list element
+  # $_ is used if loop variable is omitted
 }</code>
@@ Line 77: / Line 82: @@
   * Read a line of input - ''$line = <STDIN>;''
   * ''chomp'' removes a newline e.g. ''chomp($line=<STDIN>);''
+  * Assigning <STDIN> to a list reads all input up till EOF e.g. <code perl> chmop(@lines = <STDIN>);</code>
+===== User Subroutines =====
+  * Subroutines are in their own namespace and are typically called using ''&mysub'' (sometimes the ampersand can be omitted).
+  * Subroutines can be defined anywhere e.g. <code perl> sub mysub {
+  my($m, $n) = @_
+  $m + $n;
+} </code>
+  * The value of the last expression evaluated is returned.
+  * Arguments are in the list @_ . If ''&mysub;'' is used, the parent's argument list is inherited.
+  * Lexical scoped variables can be used in any block by prefixing with ''my''.

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