package MatchVars;

use vars qw($string $match $prematch $postmatch $_internal $_init);
$_internal = "";
$_init = 0;

sub string {
  shift if ref($_[0]) eq "MatchVars" || (@_ > 1 && $_[0] eq "MatchVars");
  return $_internal unless @_;
  $_internal = \ $_[0]
}


sub import {
  no strict;
  my $caller = caller();
  unless ($_init) {
    tie $string, "MatchVars::string", \$_internal;
    tie $match, "MatchVars::Match", \$_internal;
    tie $prematch, "MatchVars::Prematch", \$_internal;
    tie $postmatch, "MatchVars::Postmatch", \$_internal;
    $_init = 1;
  }
  *{"$caller\::_string"} = \$string;
  *{"$caller\::_match"} = \$match;
  *{"$caller\::_prematch"} = \$prematch;
  *{"$caller\::_postmatch"} = \$postmatch;
}

package MatchVars::string;

sub TIESCALAR {
    my ( $class, $r_string ) = @_; 
    bless \do{my $o = $r_string},$class;
}

sub STORE { 
  my $self = shift;
  $$$self = \ $_[0];
}

sub FETCH {
  my $self = shift;
  return $$$$self;
}

sub UNTIE { }

sub DESTROY { }

package MatchVars::base;

sub TIESCALAR {
    my ( $class, $r_string ) = @_; 
    bless \do{my $o = $r_string},$class;
}

sub STORE { }

sub UNTIE { }

sub DESTROY { }

package MatchVars::Match;

use base "MatchVars::base";

sub FETCH { 
    my $self = shift;
    no warnings;
    my $return = substr($$$$self, $-[0], $+[0] - $-[0] );
    return defined $return?$return:"";
}

package MatchVars::Prematch;

use base "MatchVars::base";

sub FETCH {
    my $self = shift;
    no warnings;
    my $return = substr($$$$self,0, $-[0] );
    return defined $return?$return:"";
}

package MatchVars::Postmatch;

use base "MatchVars::base";

sub FETCH { 
    my $self = shift;
    no warnings;
    my $return = substr($$$$self, $+[0]);
    return defined $return?$return:"";
}

1;

# END OF MatchVars.pm
__END__
#!/usr/bin/perl -wl
use strict;
use MatchVars;

# Let's try it out
my $var1 = "pre=match=post";
$_string = $var1;

print "1: $_prematch | $_match | $_postmatch" if $var1 =~ /=\w+=/;

# 1: pre | =match= | post

# But this doesn't work properly if you change $var
my $var2 = "pre=match=post";
$_string = $var2;
$var2 = "this=is_not=right";

print "2: $_prematch | $_match | $_postmatch" if $var2 =~ /=\w+=/;
# 2: pre= | match=po | st

# But this is a workaround
my $var3 = "pre=match=post";
MatchVars->string($var3);
$var3 = "this=shows=up";

print "3: $_prematch | $_match | $_postmatch" if $var3 =~ /=\w+=/;
# this | =shows= | up