I've got some legacy code that I'm dealing with. It's too much to clean up in one shot. It's using \1 inside of the s/// operator. I looked into perllexwarn and found I can shut it off with no warnings qw(syntax), but I did this with trial and error. Is there an easier way to get right from the warning to the way to shut it off?
It's doing stuff like this:
use strict;
$_ = "abc";
s/abc/\1/;
no warnings qw(syntax);
s/abc/\1/;
the message it generates is :
\1 better written as $1
Execute your script as
perl -Mdiagnostics ./a.pl
or temporarily add use diagnostics; to your script. This will produce something like
\1 better written as $1 at ./a.pl line 4 (#1)
(W syntax) Outside of patterns, backreferences live on as variables.
The use of backslashes is grandfathered on the right-hand side of a
substitution, but stylistically it's better to use the variable form
because other Perl programmers will expect it, and it works better if
there are more than 9 backreferences.
Notice the (W syntax)? The word is the warning class for which you are looking.
diagnostics gets its information from perldiag, which you could search manually instead of using use diagnostics;.
Other examples:
$ perl -Mdiagnostics -we'print undef'
Use of uninitialized value in print at -e line 1 (#1)
(W uninitialized) An undefined value was used as if it were already
[...]
$ perl -Mdiagnostics -we'no warnings qw( uninitialized ); print undef'
$ perl -Mdiagnostics -we'sub foo { } sub foo { }'
Subroutine foo redefined at -e line 1 (#1)
(W redefine) You redefined a subroutine. To suppress this warning, say
[...]
$ perl -Mdiagnostics -we'no warnings qw( redefine ); sub foo { } sub foo { }'
$
In case you're curious, the letter provided by diagnostics before the warning class is one of the following: