fix: missing string concatenation

[RalphHightower]

"(?^(2-9$))|" +
"(" +
"(?^(5[00|21|22|23|24|25|26|27|28|29|33|44|66|77|88]))|" +
"(?^(6[00|22]))|" +
"(?^(700))|" +
"(?^(710))|" +
"(?^(8[00|33|44|55|66|77|88]))|" +
"(?^(900)" +
")(?([2-9][0-9][0-9])-(?[0-9]{4}))$" +
"(?([2-9]9[0-9])|((37|96)[0-9]))-[2-9][0-9][0-9]-[0-9]{4}$" +
"(?^([2-9][0-8][0-9]))-555-(?(1212|4334))$|" +
"(?^[2-9][0-8][0-9])-555-(?(01[0-9][0-9]))$|" +
"(?([2-9][0-8][0-9]))-(?([2-9][0-9][0-9]))-(?([0-9]{4}))$";