(* ::Package:: *)
values = "
/* Generic break values */
break-before: auto;
break-before: avoid;
break-before: always;
break-before: all;
/* Page break values */
break-before: avoid-page;
break-before: page;
break-before: left;
break-before: right;
break-before: recto;
break-before: verso;
/* Column break values */
break-before: avoid-column;
break-before: column;
/* Region break values */
break-before: avoid-region;
break-before: region;
/* Global values */
break-before: inherit;
break-before: initial;
break-before: revert;
break-before: unset;
";
all = Sort@StringCases[
values,
RegularExpression[":\\s*([a-zA-Z0-9-]+);"] :> "$1"
];
"[\"" <> StringRiffle[all, "\",\""] <> "\"].contains(&mode)"