I like it. Although I think you meant:

!-p _
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-p is a test operator, so your expression is more or less equivalent to a question: "Is _ (=this) not a pipe?".

At least in Unix, '|' is not a valid filename, so -p '|' will always be false: "Is '|' a pipe? No.". So the ASCII representation of a pipe, '|', is never a pipe itself, which is exactly what Magritte meant with his painting.

I've seen this assertion several times now, though the last time was a while ago. It hasn't gotten any more correct in the interim.

$ touch \|
$ file !$
file \|
|: empty
$ ls -l \|
-rw-r--r--  1 chemboy users 0 Mar 14 00:09 |
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That, for the record, was on Gentoo Linux on a G4, but similar results can be readily obtained on other platforms.




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If God had meant us to fly, he would *never* have given us the railroads.
    --Michael Flanders

Or, taking "this" to be $_ as we do, -p and print, print q m n'est pas une pipem, $/; (yes, I mean that ;-)

It's too late now, but if perl had added a special syntax of m!! to indicate a negated match we could use m!\|!. As it is we have a modified form of one of sfink's suggestions: $_ !~ m/\|/.

Also, what about?

pipe(STDIN, STDOUT);
#Optional:
$|--, print STDOUT "This is not a pipe\n" ne <STDIN>;
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--
I'm not belgian but I play one on TV. On dit que je parle comme un belge aussi.