If -regexp is specified, the breakpoint string will be interpreted as a regular expression (regexp). The regexp syntax follows the common Perl style, as interpreted by the Hyperscan library https://hyperscan.io.
Note that the string is a Simics CLI string, and thus \ has to be escaped as \\ when writing the regexp.
Examples:
$con.break -regexp "\\d{3}"
$con.break -regexp "\\[.*4.*\\]"
$con.break -regexp "\\w{3}|[{}]{6}"
For more information about regular expression syntax, see https://perldoc.perl.org/re.html.
If -regexp is specified, then -once is ignored.