why no syntax error?

[Ronald Fischer]

I recently wrote the following nonsense:

if($arg = ~ /^\d{4}$/) { ... }

In case you don't see it immediately: I had erroneously typed a space between
the equal sign and the tilde.

To my surprise, this statement was executed without error message. $arg was set
to 294967295.

The tilde did bitwise complement of course, but on what? On a regexp? This
does not seem to make sense to me....

This was executed under Perl 5.6.1

Ronald

 

[Sherm Pendley]

I recently wrote the following nonsense:

if($arg = ~ /^\d{4}$/) { ... }

The tilde did bitwise complement of course, but on what? On a regexp? This
does not seem to make sense to me....

Pattern matching implicitly uses $_ if no other variable is used. I
expect you'd get the same results from this:

if ($arg = ~ ($_ =~ /^\d{4}$/)) { ... }

sherm--

 

[Anno Siegel]

I recently wrote the following nonsense:

if($arg = ~ /^\d{4}$/) { ... }

In case you don't see it immediately: I had erroneously typed a space between
the equal sign and the tilde.

To my surprise, this statement was executed without error message. $arg was set
to 294967295.

The tilde did bitwise complement of course, but on what? On a regexp? This
does not seem to make sense to me....

A regex that isn't bound by =~ applies to $_. That is what happens
here. The result of that match in scalar context is inverted and
assigned to $arg.

Anno