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

perl -pe 's/foo\n/foo\t/g' temp2.txt

below is the test.

243> cat temp2.txt 
foo
bar bar bar bar some text 
pearl[ncm_o12.2_int_x86.@2].244> perl -pe 's/foo\n/foo\t/g' temp2.txt
foo     bar bar bar bar some text 

Answer 2

In awk:

awk '/foo$/ { printf("%s\t", $0); next } 1'