$l =~ s/\b$t\b/$b/eg;

The 'e' is required to treat the replacement as Perl code and not a literal string. You don't want the \b's in the replacement because the replacement isn't a regex - it's normally a literal string. You can chain 'e' so that the first evaluation would produce Perl code that would, itself, be evaluated.

This is all explained in the relevant page at http://perldoc.perl.org. (Scroll down a bit to find the s/// section.)

My criteria for good software:
  1. Does it work?
  2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

In reply to Re: Can I Use Variables In A Regex? by dragonchild
in thread Can I Use Variables In A Regex? by Khatri

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