Try either of the following:

$line =~ m/^[[:upper:]]+$/    # or
$line =~ m/^\p{IsUpper}+$/

the [: ... :] is no character class, although it looks like one.
To make it (part of) a character class, you need another set of brackets around it.

don't go for   m/^[A-Z]+$/   for world peace international reasons ;-)
See   perldoc perlre   too.

Update: You might find the double negation more convenient:

$line !~ m/[[:^upper:]]/    # or
$line !~ m/\P{IsUpper}/

(think: do not match a line that contains anything that's not an uppercase letter)

Edit: corrected a number of mistakes.
Thanks especially to davido(++) for pointing out the ones I didn't find myself. Strange enough, while the necessity of the double brackets is not in doubt, I don't get any warnings when omitting them (perl5.8.3, Linux), the code just never tests true.
Another Edit: I guess that's because it looks like a character class to Perl. So why did it throw errors when davido tried it?
Another edit (and moved this discussion to the bottom of the node) -
I tried   m/[:^upper:]/;   which bypasses warnings.
Congratulations to us, we found a bug.

Cheers, Sören

In reply to Re: Recognizing all-caps line by Happy-the-monk
in thread Recognizing all-caps line by ParisR

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