JEdit is a nifty editor, but the engine that JEdit's regex tool (RE Tester) employs has several differences from perl's -- in some cases, this makes it impossible (or just annoying :) ) to compare RETester's results with perl's interpretation of a given regex.

Here's some differences, right from the gnu.regexp documentation, included with the plugin :
Unsupported Syntax Some flavors of regular expression utilities support additional escape sequences, and this is not meant to be an exhaustive list. In the future, gnu.regexp may support some or all of the following:

(?:...) pure grouping operator (Perl5)
(?=...) positive lookahead operator (Perl5)
(?!...) negative lookahead operator (Perl5)
(?#...) embedded comment (Perl5)
(?mods) inlined compilation/execution modifiers (Perl5)
\G end of previous match (Perl5)
\b word break positional anchor (Perl5)
\B non-word break positional anchor (Perl5)
\< start of word positional anchor (egrep)
\> end of word positional anchor (egrep)
[.symbol.] collating symbol in class expression (POSIX)
[=class=] equivalence class in class expression (POSIX)


Additionally, I've seen it act rather odd when using .* without an EOL anchor.

In reply to JEdit's RE Tester. (boo) by boo_radley
in thread Regular Expression GUI? by major tom

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