Perl Regex

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  • Regex Enclosed in Slashes

    /search term/

    Binding Operator

    =~

    Negative Binding Operator

    !~

    Override Case Sensitivity

    -i or /i /searchterm/i

    Pattern Matching

    /m/searchterm/ same as /searchterm/

    Prevent Interpolation of Special Characters

    \Q<text>\E

    Anchor - Search Beginning of the string

    ^ Example /^The/

    Anchor - Search End of the String

    $ Example: /searchterm\.$/

    Any Character in a search

    /h[aiou]t/ hat, hit, hot, or hut

    Does not include

    /wa[^rx]/ Does not contain war or wax

    Character set range

    [0-9] [a-z] [A-Z] [0-9a-z]

    Character Range \d and \D

    [0-9] and [^0-9]

    Character Range \w and \W

    [0-9A-Za-z_] and [^0-9A-Za-z]

    Character Range \s and \S

    [\ \t\n\r] (space,tab,newline,return)

    Character Range \b and \B

    Boundaries between words

    Character Range .

    Match Any Character

    Character Class [[:alpha:]]

    Alphabetic Characters

    Character Class [[:alnum:]]

    Alphabetic or Numeric Characters

    Character Class [[:digit:]]

    Digits 0 to 9

    Character Class [[:lower:]]

    Lowercase Letters

    Character Class [[:upper:]]

    Uppercase Letters

    Character Class [[:punct:]]

    Punctuation Characters

    Alternative Operator

    /red|blue/ or /(red)|(blue)/ or /(red|blue)/

    Quantifiers: Optional character

    ? /g?reed/ - Search for greed or reed (? is after)

    Quantifiers: May occur more than one time

    + /n+/ - Searches for n, or nn, or nnn....

    Quantifiers: May occur once, numerous times, or none

    /trees/ - Searches for tree, trees, or treess ...

    Quantifiers: Number of Instances

    {,} /\w{5}/ - Five letter word, {4,} 4 or more {3,7} 3-7 instances

    Greedy: Find the first match that occurs

    ? - "this and thus" /th.?s/ matches "this" /th.*s/ would match "this and thus" (to the last 's')

    Greedy: Find a match using as few repeats as possible, but to allow at least one repeat

    +?

    Greedy: Find a match using zero repeats if possible

    ??

    Backreferences - Results of a search

    Outside Regex :$1, $2, etc. - In Regex: \1 and \2

    Substitution Operator

    =~ s/old/new/; (Replaces old with new; first instance only)

    Global Replacement

    =~ s/old/new/g (The g at the end is for all instances)

    Modifiers: Allow string to behave like a set of multiple lines separated by the newline character

    m

    Modifiers: Ignore newline characters and the search string is treated as a single line

    s - For example '.' will now match any character, even newline characters.

    Modifiers: Replace only the last match, used with g

    \G

    Modifier: Ignore whitespace and allow comments

    x

    Transliteration: Replace each character

    =~ tr/abc/xyz/; Replaces all 'a' with 'x', all 'b' with 'y', etc.

    Transliteration: Delete extra characters

    =~ tr/ABC/ab/d; - Replace 'A' with 'a', 'B' with 'b', deletes 'C' (Without d, 'C' with 'b')

    Substitution / Transliteration Additional Delimiters

    We can use [] or <>; easier if searching for /

    Substitution / Transliteration Create Delimiters

    =~ m#searchterm#

    Search for a Delimiter, and create substrings

    split / /,$colors ($colors="r g b"; @colors=split...)

    Create string from substring

    join " ",@colors (@colors="red green blue";$colors=join...)

    Inline Comments in searches

    =~ /searchterm(?#Comment)/

    Using inline modifiers in Regex

    =~ /(?i)searchterm/ (Same as /searchterm/i)

    Regex without backreferences

    ?: - /(?:abc)?.*(def)/ - $1 will be the result from (def) not (abc)

    Lookahead

    ?= Example: =~/one (?=two)/

    Lookbehind

    ?<

    Negative Lookahead

    ?!

    Negative Lookbehind

    ?<!

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