if ($MARC_page =~ m{
    (?:020<)?            # MARC code followed by a bracket to identify
    .*?                  # followed by anything
    \|a\s                # followed by a pipe and the subfield
    (\d{13})			 # followed by a 13-digit ISBN code
}xmgs) {
    my $isbn = $1;
}

if ($MARC_page =~ m{
    245\d{0,2}         # MARC code 245 followed by 0-2 indicators
    .*?                # followed by anything
    \|a\s              # followed by a pipe and the subfield
    (.*?)              # followed by the title
    \|                 # followed by a pipe and the next subfield
}xmgs) {
    my $title = $1;
}