Answer by Zoredache for How do I match a string with symbols in a grep-kind of way?

Use single quotes (') so $nnn isn't treated as a variable. Strings with " are interpolated strings, with a ' no interpolation happens.

Heck just just look at the output when you prefeace that string with echo.

$ echo "foo:$apr1$73wJ8tiQ$HdaRYe2pUMqBf0ZpMJz6h/"foo:3wJ8tiQ/$ echo 'foo:$apr1$73wJ8tiQ$HdaRYe2pUMqBf0ZpMJz6h/'foo:$apr1$73wJ8tiQ$HdaRYe2pUMqBf0ZpMJz6h/