Σύνθετο παράδειγμα
/* scanner for a toy Pascal-like language */
%{
/* need this for the call to atof() below */
#include <math.h>
%}
DIGIT    [0-9]
ID       [a-z][a-z0-9]*
%%
{DIGIT}+    {
            printf( "An integer: %s (%d)\n", yytext,
                    atoi( yytext ) );
            }
{DIGIT}+"."{DIGIT}*        {
            printf( "A float: %s (%g)\n", yytext,
                    atof( yytext ) );
            }
if|then|begin|end|procedure|function        {
            printf( "A keyword: %s\n", yytext );
            }
{ID}        printf( "An identifier: %s\n", yytext );
"+"|"-"|"*"|"/"   printf( "An operator: %s\n", yytext );
"{"[^}\n]*"}"     /* eat up one-line comments */
[ \t\n]+          /* eat up whitespace */
.           printf( "Unrecognized character: %s\n", yytext );
%%
main()
{
    yylex();
}