How would that change the line format of the backtrace to file:line, as desired?

#!/usr/bin/perl

use Carp 'cluck';

sub foo { bar() }
sub bar { baz() }
sub baz { cluck "big error!" }

foo();

$Carp::CarpLevel = 2;

foo();

__END__
big error! at ./834994.pl line 7
    main::baz() called at ./834994.pl line 6
    main::bar() called at ./834994.pl line 5
    main::foo() called at ./834994.pl line 9
big error! at ./834994.pl line 5
    main::foo() called at ./834994.pl line 13
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