You might consider creating your own custom tag. This example is probably not well thought through, it's basically just a tweaking of the example given at the end of perlre, but I'd never tried this before so I did what came easy:)

#! 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
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