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=head1 TITLE
Eliminate =~ operator.
=head1 VERSION
Maintainer: Steve Fink <[EMAIL PROTECTED]>
Date: 22 Aug 2000
Version: 1
Mailing List: [EMAIL PROTECTED]
Number: 138
=head1 ABSTRACT
Replace EXPR =~ m/.../ with m/.../ EXPR, and similarly for s/// and
tr///. Force an explicit dereference when using qr/.../. Disallow the
implicit treatment of a string as a regular expression to match
against.
=head1 DESCRIPTION
The EXPR =~ m/.../ syntax is ugly and unintuitive, something only its
mother (awk? sed?) could love. It performs a function that is
semantically no different from other forms of argument passing. This
RFC proposes to eliminate the =~ binding operator and treat m,
tr, and s almost like regular subroutine names but with slightly
different syntax and semantics.
To illustrate the proposal by example, the current
/pattern/;
m/pattern/;
$x =~ /pattern/;
($a, $b, $c) = $x =~ /p(a)t(t)e(r)n/;
gsx =~ s/pattern/subst/gsx;
$r = qr/pattern/; $x =~ $r;
$r = "pattern"; $x =~ $r;
would become
/pattern/;
m/pattern/;
/pattern/ $x; OR /pattern/ ($x);
($a, $b, $c) = /p(a)t(t)e(r)n/ $x;
s/pattern/subst/gsx (gsx);
$r = qr/pattern/; $r->($x);
same as the previous, or $r = "pattern"; /$r/ ($x);
Specifically, all patterns behave as if they are subroutines with a
($) prototype, except they have the current syntax for their first
argument, and $1 etc. interpolation remain unchanged.
qr/.../ would produces a CODE ref that may be invoked with the pattern
to match against. It would be a regular CODE ref rather than the
current magical Regexp reference type.
=head2 RELATED WACKY IDEA #1: Everything's a reference
Alternatively, we could think of m/.../ as always returning a
reference, so that the syntax is /pattern/->($x). This is much more
visually distinctive, but runs afoul of Larry's "no implicit
dereferencing" rule in order to make /pattern/ default to
/pattern/->($_). On the other hand, $a =~ $b already breaks that rule
by dereferencing qr// refs, so maybe it's not such a big deal.
=head2 RELATED WACKY IDEA #2: Creating references to matching operations
Now forget about the previous alternative and assume as in the main
section that we have /pattern/ ($x) and qr/pattern/->($x). This
naturally leads to \m/pattern/ or \&m/pattern/ as an equivalent for
qr/pattern/, and also introduces \s/pattern/subst/ and
\tr/pattern/subst/ as new reference types.
=head1 IMPLEMENTATION
Minor parser changes. Currently, the relevent rule in perly.y is
B<C<term MATCHOP term>>. The terms would be reversed, and the first
would
need to be renamed to cover only s///, m//, and tr/// (and
equivalents). So it would be something like B<C<matchterm term>>.
=head1 REFERENCES
=head2 Contributors
Dirk Meyers <[EMAIL PROTECTED]> came up with this idea.
