use strict;
use warnings;
use Data::Dumper;
use Benchmark;
# verification pattern is used by the developer to set a range
# in this case the first letter before the slash is to verify
# the attribute name in $attrs. The content after the slash
# is used to verify the attribute was not used yet. but in the full
# version ere is a range that goes to a function to verify the
# attribute values.
my $match_list = 'a/ere,c/ere,d/ere';

# in $attrs the letter before equal is the attribute name
# and needs to be compared with $match_list for its value to be replaced.
# all attribute names can only be used one time in $attrs to be good
# the value of the attribute may have a space in it.
my $attrs = 'TY a=errt c=rrr dd d=rrr dd'; # example that should convert
#my $attrs = 'TY a=errt c=rrr dd d=rrr d=du 0'; # example that should say "nope"

# tag name, just something that is there.
my $tag = 'TY';

# markup is the template of the output if its good
my $markup = 'TY:X{a} X{c}|X{d}';

# few more examples based off some of your posts
sub third_draft {
    my %xlist = map{ split('\/', $_) } split(',', $match_list);

    $attrs =~ s/\A$tag //; # clean up
    for (split (' (?=\w+\=)', $attrs)) {
     my ($name, $value) = split('=');
     # only one attribute of the same name is allowed.
     if (defined $xlist{$name}) {
      $xlist{$name} = undef; # this exists now
      $markup =~ s/X\{$name\}/$value/g;
     }
       else { # fails get nothing and end.
        $markup = '';
        last;
       }
     }

     # not in Benchmark
#     $markup
#     ? print $markup
#     : print 'nope';
}

sub second_draft {
    my %xlist = map{ split(/\//, $_) } # make list
    split(/,/, $match_list);

    $attrs =~ s/\A$tag //; # clean up
    my @attr = $attrs =~ /(?:\A| )(.+?)(?=(?: \w+=|\z))/g; # make array for xlist
    for (@attr) {
     my ($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
      $markup =~ s/X\{$name\}/$value/g;
     }
      else { # fails get nothing and end.
       $markup = '';
       last;
       }
     }
     # not in Benchmark
#     $markup
#     ? print $markup
#     : print 'nope';
}

sub first_draft {
    my %xlist = map{ split(/\//, $_, 2) } # make list
    grep{ m/\// } split(/,/, $match_list);

    $attrs =~ s/\A$tag //; # clean up
    my @attr = $attrs =~ /(?:\A| )(.+?)(?=(?: \w+=|\z))/g; # make array for xlist
    for (@attr) {
     my ($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
      $markup =~ s/X\{$name\}/$value/g;
     }
      else { # fails get nothing and end.
       $markup = '';
       last;
       }
     }
     # not in Benchmark
#     $markup
#     ? print $markup
#     : print 'nope';
}
     timethese($ARGV[0] || -1, {
    1 ?  (
        'a_first_draft'  => \&first_draft,
    ) : (),
    1 ?  (
        'b_second_draft'  => \&second_draft,
    ) : (),
    1 ?  (
        'c_third_draft'  => \&third_draft,
    ) : (),
});