Difference between regexpatch and xpatch

Question

I'm trying to put individual names within my bibliographic entries into brackets, and trying to patch biblatex bibmacros for that, using the facilities of (rege)xpatch.

In particular, I'm trying to patch the bibmacros name:given-family and name:family-given.

As far as I understood, regexpatch offers the same patch commands xpatch does, plus some with regex features. And I couldn't grasp from the documentation any change of syntax of the original commands of xpatch whithin regexpatch. However, the patches which work with xpatch return undefined control sequence with regexpatch. A MWE:

\documentclass{article}

\usepackage{xpatch}
%\usepackage{regexpatch}

\usepackage[style=authortitle]{biblatex}
\addbibresource{biblatex-examples.bib}

% These patches work with xpatch, but not with regexpatch
\xpatchbibmacro{name:given-family}
    {\usebibmacro{name:hook}}
    {\bibopenbracket\usebibmacro{name:hook}}
    {}{}

\xapptobibmacro{name:given-family}
    {\bibclosebracket}
    {}{}

\xpatchbibmacro{name:family-given}
    {\usebibmacro{name:hook}{#3#1}}
    {\bibopenbracket\usebibmacro{name:hook}{#3#1}}
    {}{}

\xpatchbibmacro{name:family-given}
    {\usebibmacro{name:hook}{#1}}
    {\bibopenbracket\usebibmacro{name:hook}{#1}}
    {}{}

\xapptobibmacro{name:family-given}
    {\bibclosebracket}
    {}{}

\begin{document}

\nocite{*}

\printbibliography

\end{document}

What am I missing/doing wrong?

Obs: I need regexpatch for other patches that actually require the regex facilities, and I'd like to use the original xpatch patch commands, if possible, for the sake of code readability.

Answer 1

You've discovered a hidden feature. ;-)

This should fix the temporary issue.

\documentclass{article}

%\usepackage{xpatch}
\usepackage{regexpatch}

% Fix regexpatch itself
\ExplSyntaxOn
\makeatletter
\exp_args:Nc \xpatchcmd { xpatchbibmacro~code }
 {\xpatch_main:Ncnnnn}
 {\xpatch_main_four:Ncnnnn}
 {}{}
\makeatother
\ExplSyntaxOff

\usepackage[style=authortitle]{biblatex}
\addbibresource{biblatex-examples.bib}

% These patches work with xpatch, but not with regexpatch
\xpatchbibmacro{name:given-family}
    {\usebibmacro{name:hook}}
    {\bibopenbracket\usebibmacro{name:hook}}
    {}{}

\xapptobibmacro{name:given-family}
    {\bibclosebracket}
    {}{}

\xpatchbibmacro{name:family-given}
    {\usebibmacro{name:hook}{#3#1}}
    {\bibopenbracket\usebibmacro{name:hook}{#3#1}}
    {}{}

\xpatchbibmacro{name:family-given}
    {\usebibmacro{name:hook}{#1}}
    {\bibopenbracket\usebibmacro{name:hook}{#1}}
    {}{}

\xapptobibmacro{name:family-given}
    {\bibclosebracket}
    {}{}

\begin{document}

\nocite{*}

\printbibliography

\end{document}