Language Comparison

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A brief comparison of language lookbehind syntaxes with links to their manuals.

Language	Syntax	Variable Length	Docs
Perl	(?<=pattern)	No	http://perldoc.perl.org/perlre.html#(?%3C=pattern)-\K
Perl	\K	Yes?	http://perldoc.perl.org/perlre.html#(?%3C=pattern)-\K
.NET	(?<=pattern)	?	https://msdn.microsoft.com/en-us/library/bs2twtah(v=vs.110).aspx#zerowidth_positive_lookbehind_assertion
Python	(?<=pattern)	No	https://docs.python.org/3/library/re.html#re-syntax
Ruby	(?<=pattern)	No	https://ruby-doc.org/core-2.2.0/Regexp.html#class-Regexp-label-Anchors
Go / RE2	unsupported		https://golang.org/pkg/regexp/ / https://github.com/google/re2/wiki/Syntax
Rust	unsupported		https://doc.rust-lang.org/regex/regex/index.html
PHP	(?<=pattern)	No	https://secure.php.net/manual/en/regexp.reference.assertions.php

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