Removing new line after a particular text via bash/awk/sed/perl

Question

I would like to remove all the newline character that occurs after a partiular string and replace it with a tab space. Say for instance my sample.txt is as follows

Answer 1

Mmm. not sure this fits your requirements, but I'd do this in vim:

:g/^foo$/join

Or, if foo could be anywhere on a line:

:g/foo$/join

Of course, :%s/foo\n/foo\t/g will do nicely too