my $rxLine = qr
   {(?xs)           # Use extended regular expression syntax (x)
                    #   allowing whitespace in the pattern for
                    #   readability, and comments. Allow the .
                    #   (regexp wildcard metacharacter) to match
                    #   a newline (s)
       ^            # Anchor pattern to start of string
       (            # Open capture group (1st)
           [^{};]+  # Negated character class, anything except {, }
                    #   or ; characters. + quantifier is 1 or more
                    #   of, greedy matching so will match as many
                    #   as possible
           [{};]    # Character class, any of {, } or ; characters.
                    #   No quantifier so exactly 1 of
       )            # Close capture group (1st)
       (            # Open capture group (2nd)
           \s*      # Whitespace character. * quantifier is 0 or more
                    #   of, greedy
           \S+      # Non-whitespace character. 1 or more, greedy
           .*       # Any character (including newline because of the
                    #   s modifier). 0 or more, greedy
       )            # Close capture group (2nd)
       $            # Anchor pattern to end of string
   };

if( $line =~ $rxLine )
{
    # Do something here
}