Regex_modifiers='ms' 'cd' # non-greedy '. Regex_modifiers='m' 'cd' # matches second lineĪbXd' # '.' matches newline, so the end of string is reached Regex_modifiers='ms' 'cd' # matches newline, /m, /s modifiers do not matter Regex_modifiers='s' 'cd' # matches newline, /m, /s modifiers do not matter Regex_modifiers='m' 'cd' # matches newline, /m, /s modifiers do not matter Regex_modifiers='' 'cd' # matches newline, /m, /s modifiers do not matter Regex_modifiers='ms' 'cd' # non-greedy '.*?' causes '$' to match the first newline Fortunately the grouping and alternation facilities provided by the regex engine are very capable, but when all else fails we can just perform a second match using a separate regular expression supported by the tool or native. Regex_modifiers='m' 'cd' # '$' matches first newlineĪbcd' # '.' matches newline, so the end of string is reached When attempting to build a logical or operation using regular expressions, we have a few approaches to follow. Regex_modifiers='' # '.' does not match newline, cannot reach end of string Regex_modifiers='ms' 'cd' # /m, /s modifiers do not matter in single-line string Regex_modifiers='s' 'cd' # /m, /s modifiers do not matter in single-line string Regex_modifiers='m' 'cd' # /m, /s modifiers do not matter in single-line string Principle 2: The maximal matching quantifiers '?', '*', '+' and That allows a match for the whole regexp will be the one used. Principle 0: Taken as a whole, any regexp will be matched at theĮarliest possible position in the string. The principles above to predict which way the regexp will match: Introduction to regexes in Perl a Just an a character. I hope this Regex Cheat-sheet will provide such aid for you. When a regexp can match a string in several different ways, we can use Perl 5 Regex Cheat sheet When learning regexes, or when you need to use a feature you have not used yet or dont use often, it can be quite useful to have a place for quick look-up. (with 2 registered patches, see perl -V for more detail) This is perl 5, version 18, subversion 4 (v5.18.4) built for darwin-thread-multi-2level S/^(*)(B.*?)$/>$1|$2aaaa|BaBaBBbbbb|Bbadbeeeee|Beeeeeaaaa|BaBaBBbbbb|Bbadbecccc Thus, with the following code: #!/usr/bin/perl PCRE Versions PCRE Enhancements New Regular Expression Functions PCRE Syntax. That is, change "^" and "$" from matching the start of the string's first line and the end of its last line to matching the start and end of each line within the string. Perl Compatible Regular Expressions (PCRE) Documentation. Treat the string being matched against as multiple lines. This is related to perl multiline regex to separate comments within paragraphs,īut focuses exclusively on a single question of regex syntax.
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