perl regular expressions

Perl regular expressions (also known as regex or regexp) are a powerful and flexible way to match and manipulate text in Perl programming language. Perl provides built-in support for regular expressions, allowing you to search for patterns, replace text, and extract information from strings.

Some of the basic syntax for using Perl regular expressions are:

1. Matching a string:

$string =~ /pattern/

This will match the regular expression pattern against the string $string and return true if there is a match.

2. Substituting a string:

$string =~ s/pattern/replacement/

This will replace the first occurrence of the regular expression pattern in the string $string with the replacement string.

3. Global substitution:

$string =~ s/pattern/replacement/g

This will replace all occurrences of the regular expression pattern in the string $string with the replacement string.

4. Character classes:

/[abc]/    # matches a, b, or c
/[^abc]/   # matches any character except a, b, or c
/\d/      # matches a digit
/\D/      # matches a non-digit
/\w/      # matches a word character (alphanumeric or underscore)
/\W/      # matches a non-word character

5. Quantifiers:

/a+/      # matches one or more "a"s
/a*/      # matches zero or more "a"s
/a?/      # matches zero or one "a"
/a{3}/    # matches exactly three "a"s
/a{3,5}/  # matches three to five "a"s
/a{3,}/   # matches three or more "a"s

These are just some of the basic syntax for using Perl regular expressions. Regular expressions can be very powerful and complex, allowing you to match very specific patterns in text.