NAME
Regexp::Deferred - defer execution of (?{}) codeblock until end of match
SYNOPSIS
use Regexp::Deferred;
"foobar" =~
/(?:foo (?{ warn "matched foo!" }) ) d
|
(?:bar (?{ warn "matched bar!"}) )
/x;
__END__
matched bar!DESCRIPTION
The Perl regular expression engine provides a special embedded pattern, (?{ <code> }), that immediately executes <code> when the pattern is used during the matching process. In the SYNOPSIS example, the initial foo pattern is initially matched by the regular expression engine, and the associated code would normally be executed immediately. Regexp::Deferred overrides the qr function such that all of the code blocks get deferred until the very end of the match, at which time only the blocks participating in the overall successful match are executed.
That doesn't sound like much, but it does allow you to change this:
if(m/ (fee) .* (fie) .* (foe) .* (fum) /x) {
($fee, $fie, $foe, $fum) = ($1, $2, $3, $4);
}into:
use Regexp::DeferredExecution;
m/ (fee) (?{ $fee = $^N }) .*
(fie) (?{ $fie = $^N }) .*
(foe) (?{ $foe = $^N }) .*
(fum) (?{ $fum = $^N })
/x;Which means that adding new sets of capturing parentheses doesn't require the counting exercise to figure out which set is $1, $2, etc.
Of course this mechanism isn't specific to assigning from $^N; there's no doubt a bunch of other clever things you can do with this as well; I'll let you know as I run into them.
USAGE
Like any other package that overload core functionality, you can turn it on and off via "use" and "no" statements.
BUGS
Note that currently, only the currently active $^N matching variable is stored for delayed access (e.g. don't try to access other special regexp variables from within a (?{}) code block, because they might not be as you'd expect).
None so far, but it's still early.
TODO
When closures can be compiled from within (?{}) constructs, all the special variables will become available and this will all be much simpler.
AUTHOR
Aaron J. Mackey <amackey@virginia.edu>