Spurious unbalanced error

[CeleritasCelery]

Using the test file below with the cursor located at | try to type the m character.

#!/usr/bin/perl
|
my $foo;

You will see the error End of ‘mp ... p’ string/RE not found: (scan-error Unbalanced parentheses n n)

[choroba]

That's the expected behaviour, as cperl-mode can't find the closing | for a m|...| match.

[CeleritasCelery]

I realize now that using | to indicate the cursor position was a mistake. The file looks like this

#!/usr/bin/perl

my $foo;

there is no | in the file. typing m (as in starting to type the keyword my) before my $foo leads to the error. However typing the letter m after my $foo does not lead to the error. In either case, there are no unbalanced parenthesis.

[choroba]

There are. Try it with a variable name that contains m:

#!/usr/bin/perl
m
my $foo_m;

As running perl -MO=Deparse on the source tells us, it's equivalent to

/y $foo_/;

because perlop:

When using a character valid in an identifier, whitespace is required after the "m".

[CeleritasCelery]

Wow. You are right. Since this issue doesn't throw an error (just prints), its manageable. It would be nice however, if the major mode either suppressed this error or found a better way to handle it, as it's quite confusing if you do not know what is going on.