#! perl -slw
use strict;
package CustomReTag;
use overload;

sub import {
shift;
	die "No argument to customre::import allowed" if @_;
	overload::constant 'qr' => \&convert;
}

sub invalid { die "/$_[0]/: invalid escape '\\$_[1]'"}

my %rules = (
	'\\' => '\\',
	'Y|' => qr/<\w\w>/
);

sub convert {
	my $re = shift;
	$re =~ s{ \\ ( \\ | Y . ) }
	        { $rules{$1} or invalid($re,$1) }sgex;
	return $re;
}

package main;

my $s = '<5b>I <5c>like <5d>tacos';

my $re = CustomReTag::convert '(\Y|tacos)';

$s =~ s[$re][yummy $1]g;

print $s;

__END__
P:\test>junk
<5b>I <5c>like yummy <5d>tacos