Note that the rel2abs approach will only give the same result if / is the CWD. Otherwise it's a different result:

#!/usr/bin/env perl
use strict;
use warnings;
use File::Spec;

chdir '/tmp';
my $path = './root/git/common/crt_del/cert/DEFAULT.pem';

$path = File::Spec->rel2abs ($path)
  unless File::Spec->file_name_is_absolute ($path);
print "$path\n";
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