You could do this:

use strict;
use warnings;
use Carp;

# Configure the warn signal handler to print the stack trace provided 
+by Carp.
$SIG{__WARN__} = sub {print STDERR Carp::longmess(@_); };

run();

sub run {
    my $code = eval 'sub {
        my $a = 1 - undef;
    };';
    $code->();
}
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The output is:

Use of uninitialized value in subtraction (-) at (eval 1) line 2.
        main::__ANON__() called at pm564376.pl line 14
        main::run() called at pm564376.pl line 8
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