This is 6x faster than your original and 50% faster than your latest (and a whole lot more readable to boot):

use strict;
use warnings;
use Data::Dump qw[ pp ];
use Benchmark qw[ cmpthese ];

my $match_list  = 'a/ere,b/ere,c/ere,d/ere,e/ere,f/ere,g/ere,h/ere';
my @markup      = ( 'TY:' .  'X{a} X{b} X{c} X{d} X{e}  X{f} X{g} X{h}
+ ' x 100 ) x 3;
my @attrs       = ( 'TY a=alpha b=bravo c=charlie d=delta e=echo f=fox
+trot g=golf h=hotel' ) x 3;
my $tag         = 'TY';

my $iters = $ARGV[ 0 ] // -1;

sub buk {
    my %xlist = map split( m'/', $_ ), split ',', $match_list;

    $attrs[ 0 ] =~ s[^$tag ][];

    for( split m' ', $attrs[ 0 ] ) {
        my( $name, $value ) = split '=';

        ( defined $xlist{ $name } && $markup[ 0 ] =~ s[X\{$name\}][$va
+lue]g ) 
            or $markup[ 0 ] = '', last;

        undef $xlist{ $name };
    }
    $iters ==  1 and print "0:$markup[ 0 ]\n"
}



sub first_draft {
    my %xlist = map{ split m[/], $_, 2  } grep{ m[/] } split ',', $mat
+ch_list;

    $attrs[ 1 ] =~ s[\A$tag ][]; # clean up

    my @attr = $attrs[ 1 ] =~ m[(?:\A| )(.+?)(?=(?: \w+=|\z))]g;
    for( @attr ) {
        my( $name, $value ) = split '=', $_;
        # only one attribute of the same name is allowed.
        if( exists $xlist{ $name } && defined $xlist{ $name } ) {
            $xlist{ $name } = undef; # this exists now
            $markup[ 1 ] =~ s[X\{$name\}][$value]g;
        }
        else { # fails get nothing and end.
            $markup[ 1 ] = '';
            last;
        }
    }
    $iters ==  1 and print "1:$markup[ 1 ]\n"
}

sub forth_draft {
    my %xlist = map{ split('\/', $_) } split(',', $match_list);

    $attrs[ 2 ] =~ s/\A$tag //; # clean up

    for (split (' (?=\w+\=)', $attrs[ 2 ])) {
     my ($name, $value) = split('=');
     # little more golfing action
     (defined $xlist{$name} && $markup[ 2 ] =~ s/X\{$name\}/$value/g)
      ? $xlist{$name} = undef # this exists now
      : $markup[ 2 ] = '' if $markup[ 2 ]; # do this and let it run th
+rough, faster.
      last if !$markup[ 2 ]; # with out this it drops speed now?
     }
    $iters ==  1 and print "2:$markup[ 2 ]\n"
}

cmpthese(
    $iters, {
        'first_draft'  => \&first_draft,
        'forth_draft'  => \&forth_draft,
        buk => \&buk,
    }
);

__END__
C:\test>junk -1
               Rate first_draft forth_draft         buk
first_draft  4640/s          --        -79%        -86%
forth_draft 22226/s        379%          --        -33%
buk         33339/s        619%         50%          --
[download]