Perl-based Regular Expression Pattern
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A Perl-based Regular Expression Pattern is a regular expression pattern expressed in a Perl language.
- AKA: Perl Regular Expression.
- Context:
- It can be used in a Perl-based Regular Expression Replace Statement, such as
s/a([bc])d/x$1y/g;
. - …
- It can be used in a Perl-based Regular Expression Replace Statement, such as
- Example(s):
- …
- Counter-Example(s):
- See: Perl Coding Notes, Regular Expression Statement.
Examples
Jukka Korpela Examples
http://www.cs.tut.fi/~jkorpela/perl/regexp.html
expression | matches... |
---|---|
abc |
abc (that exact character sequence, but anywhere in the string) |
a.c\. |
an a followed by any single character (not newline) followed by a c followed by a period
|
a?b*c+ |
zero or one a s followed by zero or more b s followed by one or more c s.
|
^abc|abc$ |
the string abc at the beginning or at the end of the string
|
ab{2,4}c |
an a followed by two, three or four b ’s followed by a c
|
ab{2,}c |
an a followed by at least two b ’s followed by a c
|
.{81,} |
a line with at least 80 chars |
[abc] |
any one of a , b and c |
[Aa]bc |
either of Abc and abc |
[abc]+ |
any (nonempty) string of a ’s, b ’s and c’s (such as a , abba , acbabcacaa ) |
[^abc]+ |
any (nonempty) string which does not contain any of a , b and c (such as defg ) |
\d\d |
any two decimal digits, such as 42 ; same as \d{2} |
\w+ |
a “word”: a nonempty sequence of alphanumeric characters and low lines (underscores), such as foo and 12bar8 and foo_1
|
100\s*mk |
the strings 100 and mk optionally separated by any amount of white space (spaces, tabs, newlines) |
abc\b |
abc when followed by a word boundary (e.g. in abc! but not in abcd ) |
perl\B |
perl when not followed by a word
boundary (e.g. in perlert but not in perl stuff ) |
References
2011
- http://en.wikipedia.org/wiki/Regular_expression#Perl-derivative_regular_expressions
- Perl has a more consistent and richer syntax than the POSIX basic (BRE) and extended (ERE) regular expression standards. An example of its consistency is that
\
always escapes a non-alphanumeric character. Other examples of functionality possible with Perl but not POSIX-compliant regular expressions is the concept of lazy quantification (see the next section), possessive quantifies to control backtracking, named capture groups, and recursive patterns. … many other utilities and programming languages have adopted syntax similar to Perl's — for example, Java, JavaScript, PCRE, Python, Ruby, Microsoft's .NET Framework, and the W3C's XML Schema all use regular expression syntax similar to Perl's.
- Perl has a more consistent and richer syntax than the POSIX basic (BRE) and extended (ERE) regular expression standards. An example of its consistency is that