my @chunks = $sysex_dump =~ /\xF0C.[~z]((?:..LM  0087[A-Z][A-Z].+?)+)\xF7/gs;
my @parts;

for (@chunks)
{
    push @parts, $1 while /(..LM  0087[A-Z][A-Z].+?)/gs;
}

##</code><code>##

  (..LM  0087[A-Z][A-Z].+?)
#  ^^ <= here they are

##</code><code>##

/\xF0C.[~z](\.\.LM  0087[A-Z][A-Z].+?)+\xF7/s