ken@ganymede: ~/tmp
$ perl -Mstrict -Mwarnings -E '
> my $line = q{blah blah https://abc.net/cm/one blah blah};
> my $old_url = q{https://abc.net/cm/one};
> my $new_url = q{https://abcde.net/dm/two};
> $line =~ s/$old_url/$new_url/g;
> say $line;
> '
blah blah https://abcde.net/dm/two blah blah