Sub, schmub. Overload is your (evil) friend . . .

Update: Of course for efficiency you might want to check if UNIVERSAL::isa( $other, "CatCode" ) and pull out its coderef from $other->{_code}.

Update: Another tweak. To paraphrase Homer Simpson, "In America first joo geet dee syntactic shoooogar, dehn joo geet dee powah, dehn joo geet de wimin."

Update: And even more silliness, buscc that reverses the call order (new code called first then the old code).

#!/usr/bin/perl
BEGIN {
## This would really be in CatCode.pm . . .
package CatCode;

use UNIVERSAL qw( isa );
use overload "." => "_cat_sub",
             "&{}" => "_call_sub";

require Exporter;
@CatCode::ISA = qw( Exporter );
@CatCode::EXPORT_OK = qw( ccsub );

sub ccsub (&) { return CatCode->new( shift() ); }

sub new {
  my $class = shift;    
  my $code = shift;

  return bless { _code => $code }, $class;
}

sub _cat_sub {
  my( $self, $other ) = @_;

  my $oldcode = $self->{_code};

  if( isa( $other, "CatCode::Reverse" ) ) {
    $other = $other->{_code};
    $self->{_code} = sub { $other->( @_ ); $oldcode->( @_ ); };
  } elsif( isa( $other, "CatCode" ) ) {
    $other = $other->{_code};
    $self->{_code} = sub { $oldcode->( @_ ); $other->( @_ ) };
  } else {
    $self->{_code} = sub { $oldcode->( @_ ); $other->( @_ ) };
  }

  return $self;
}

sub _call_sub { my $self = shift; sub { $self->{_code}->( @_ ) } }

package CatCode::Reverse;

@CatCode::Reverse::ISA = qw( CatCode );
@CatCode::Reverse::EXPORT_OK = qw( buscc );

sub buscc (&) { CatCode::Reverse->new( shift() ); }

1;

}

package main;

BEGIN { CatCode->import( qw( ccsub ) )}
BEGIN { CatCode::Reverse->import( qw( buscc ) )}

my $cc = ccsub { print "one $_[0]\n" };

$cc .= sub { print "two $_[0]\n" };

$cc .= buscc { print "three $_[0]\n" };

$cc .= sub { print "four $_[0]\n" };

$cc->( "fish" );

exit 0

__END__
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