%option noyywrap

%%

[0-9][a-zA-Z0-9_]+        { printf("Invalid Identifier: %s (cannot start with digit)\n", yytext); }

[@#$%^&*\-+][a-zA-Z0-9_]*  { printf("Invalid Identifier: %s (cannot start with special character)\n", yytext); }

[ \t\n]+    ; 

%%

int main() {
    printf("Enter input:\n");
    yylex();
    return 0;
}