Here’s my .l file.

%{
# include <stdio.h>
%}


DIGIT   [0-9]+

caps    [A-Z]+
low [a-z]+


%%

"""        printf("#");
","     printf("|");
{low}       printf("_");
{caps}      printf("A");
{DIGIT}     printf("0");

Here’s my input:

" "
ajdljeohfgf
ODSHJOJEHEEW
894930248
"abdef"
"987987"
"EWGGEWR"
"wroegu2948t24t

Here’s what I say I should be getting:

# #
_
A
0
#_#
#0#
#A#
#_0_0_

Here’s what I am getting:

# #
_
A
0
#abdef#
#987987#
#EWGGEWR#
#wroegu2948t24_

That is, the quotes appear to be turning character classes on and off in some weird fashion. As one example, “abdef” ought to become (so I say) #_#, but it doesn’t. I’ve never seen such weirdness. My flex says it’s version 2.5.4. My locale says:

:~$ locale
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

and I admit that I’m accustomed to the C locale, but, heavens to Betsy! The first time it sees lower or upper, it matches like I expect, and then decides to stop matching at all?
What is going on?
Ubuntu 24.04, latest patches.

New info, it’s definitely character classes. if I stop using named character classes, it does what i expect.

%%

"""        printf("#");
","     printf("|");
[a-z]+      printf("_");
[A-Z]+      printf("A");
[0-9]+      printf("0");

THAT WORKS LIKE I EXPECT. But I cannot understand why using the named char classes fails.