Hmm, I'm not sure... I can't reproduce your problem...

$_ = '11/29/2001';

# First I tried this...
# s,/,\\/,g;

s{/}{\\/}g;

print;
[download]

On my system, at least, both substitutions print 11\/29\/2001.

"We're experiencing some Godzilla-related turbulence..."