in reply to Replace all at once

I'm aware that i can replace, using a regex, a whole bunch of characters with their equivalent characters using tr///;

First, tr is not a regular expression. The two bear a passing resemblance due to syntax, but they are very different beasts.

Now in your example:   $text =~ tr^m,n^|\/|,/\/^; there are more charactes on the right than there are on the left.

In Section Seekers of Perl Wisdom